Update module github.com/prometheus/client_golang to v0.9.4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
github.com/prometheus/client_golang	require	patch	v0.9.1 -> v0.9.4

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Release Notes

prometheus/client_golang

### [`v0.9.4`](https://togithub.com/prometheus/client_golang/releases/v0.9.4) [Compare Source](https://togithub.com/prometheus/client_golang/compare/v0.9.3...v0.9.4) - \[CHANGE] API client: Switch to alert values as strings. [#​585](https://togithub.com/prometheus/client_golang/issues/585) - \[FEATURE] Add a collector for Go module build information. [#​595](https://togithub.com/prometheus/client_golang/issues/595) - \[FEATURE] promhttp: Add an counter for internal errors during HTTP exposition. [#​594](https://togithub.com/prometheus/client_golang/issues/594) - \[FEATURE] API client: Support target metadata API. [#​590](https://togithub.com/prometheus/client_golang/issues/590) - \[FEATURE] API client: Support storage warnings. [#​562](https://togithub.com/prometheus/client_golang/issues/562) - \[ENHANCEMENT] API client: Improve performance handling JSON. [#​570](https://togithub.com/prometheus/client_golang/issues/570) - \[BUGFIX] Reduce test flakiness. [#​573](https://togithub.com/prometheus/client_golang/issues/573) ### [`v0.9.3`](https://togithub.com/prometheus/client_golang/releases/v0.9.3) [Compare Source](https://togithub.com/prometheus/client_golang/compare/v0.9.2...v0.9.3) - \[CHANGE] Required Go version is now 1.9+. [#​561](https://togithub.com/prometheus/client_golang/issues/561) - \[FEATURE] API client: Add POST with get fallback for Query/QueryRange. [#​557](https://togithub.com/prometheus/client_golang/issues/557) - \[FEATURE] API client: Add alerts endpoint. [#​552](https://togithub.com/prometheus/client_golang/issues/552) - \[FEATURE] API client: Add rules endpoint. [#​508](https://togithub.com/prometheus/client_golang/issues/508) - \[FEATURE] push: Add option to pick metrics format. [#​540](https://togithub.com/prometheus/client_golang/issues/540) - \[ENHANCEMENT] Limit time the Go collector may take to collect memstats, returning results from the previous collection in case of a timeout. [#​568](https://togithub.com/prometheus/client_golang/issues/568) - \[ENHANCEMENT] Pusher now requires only a thin interface instead of a full `http.Client`, facilitating mocking and custom HTTP client implementation. [#​559](https://togithub.com/prometheus/client_golang/issues/559) - \[ENHANCEMENT] Memory usage improvement for histograms and summaries without objectives. [#​536](https://togithub.com/prometheus/client_golang/issues/536) - \[ENHANCEMENT] Summaries without objectives are now lock-free. [#​521](https://togithub.com/prometheus/client_golang/issues/521) - \[BUGFIX] promhttp: `InstrumentRoundTripperTrace` now takes into account a pre-set context. [#​582](https://togithub.com/prometheus/client_golang/issues/582) - \[BUGFIX] `TestCounterAddLarge` now works on all platforms. [#​567](https://togithub.com/prometheus/client_golang/issues/567) - \[BUGFIX] Fix `promhttp` examples. [#​535](https://togithub.com/prometheus/client_golang/issues/535) [#​544](https://togithub.com/prometheus/client_golang/issues/544) - \[BUGFIX] API client: Wait for done before writing to shared response body. [#​532](https://togithub.com/prometheus/client_golang/issues/532) - \[BUGFIX] API client: Deal with discovered labels properly. [#​529](https://togithub.com/prometheus/client_golang/issues/529) ### [`v0.9.2`](https://togithub.com/prometheus/client_golang/releases/v0.9.2) [Compare Source](https://togithub.com/prometheus/client_golang/compare/v0.9.1...v0.9.2) - \[FEATURE] Support for Go modules. [#​501](https://togithub.com/prometheus/client_golang/issues/501) - \[FEATURE] `Timer.ObserveDuration` returns observed duration. [#​509](https://togithub.com/prometheus/client_golang/issues/509) - \[ENHANCEMENT] Improved doc comments and error messages. [#​504](https://togithub.com/prometheus/client_golang/issues/504) - \[BUGFIX] Fix race condition during metrics gathering. [#​512](https://togithub.com/prometheus/client_golang/issues/512) - \[BUGFIX] Fix testutil metric comparison for Histograms and empty labels. [#​494](https://togithub.com/prometheus/client_golang/issues/494) [#​498](https://togithub.com/prometheus/client_golang/issues/498)

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