chore(deps): update dependency prometheus_client to v0.21.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
prometheus_client	==0.17.0 -> ==0.21.0

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Release Notes

prometheus/client_python (prometheus_client)

### [`v0.21.0`](https://redirect.github.com/prometheus/client_python/releases/tag/v0.21.0): 0.21.0 / 2024-09-20 [Compare Source](https://redirect.github.com/prometheus/client_python/compare/v0.20.0...v0.21.0) #### What's Changed \[CHANGE] Reject invalid (not GET or OPTION) HTTP methods. [#​1019](https://redirect.github.com/prometheus/client_python/issues/1019) \[ENHANCEMENT] Allow writing metrics when holding a lock for the metric in the same thread. [#​1014](https://redirect.github.com/prometheus/client_python/issues/1014) \[BUGFIX] Check for and error on None label values. [#​1012](https://redirect.github.com/prometheus/client_python/issues/1012) \[BUGFIX] Fix timestamp comparison. [#​1038](https://redirect.github.com/prometheus/client_python/issues/1038) ### [`v0.20.0`](https://redirect.github.com/prometheus/client_python/releases/tag/v0.20.0): 0.20.0 / 2024-02-14 [Compare Source](https://redirect.github.com/prometheus/client_python/compare/v0.19.0...v0.20.0) #### What's Changed - \[CHANGE/BUGFIX] Update OpenMetrics Content Type to 1.0.0. [#​997](https://redirect.github.com/prometheus/client_python/issues/997) - \[FEATURE] Enable graceful shutdown for start\_{http,wsgi}\_server by returning the server and thread. [#​999](https://redirect.github.com/prometheus/client_python/issues/999) - \[FEATURE] Allow resetting counter metrics. [#​1005](https://redirect.github.com/prometheus/client_python/issues/1005) - \[BUGFIX] wsgi server: address family discovery is not quite right. [#​1006](https://redirect.github.com/prometheus/client_python/issues/1006) ### [`v0.19.0`](https://redirect.github.com/prometheus/client_python/releases/tag/v0.19.0): 0.19.0 / 2023-11-20 [Compare Source](https://redirect.github.com/prometheus/client_python/compare/v0.18.0...v0.19.0) #### What's Changed \[FEATURE] support HTTPS/TLS in start_http_server. [#​946](https://redirect.github.com/prometheus/client_python/issues/946) \[BUGFIX] fix: error in determining timestamp less than. [#​979](https://redirect.github.com/prometheus/client_python/issues/979) ### [`v0.18.0`](https://redirect.github.com/prometheus/client_python/releases/tag/v0.18.0): 0.18.0 / 2023-10-30 [Compare Source](https://redirect.github.com/prometheus/client_python/compare/v0.17.1...v0.18.0) \[CHANGE] Remove support for Python versions < 3.8. [#​936](https://redirect.github.com/prometheus/client_python/issues/936) \[FEATURE] Add `mostrecent` aggregation to Gauge. [#​967](https://redirect.github.com/prometheus/client_python/issues/967) \[ENHANCEMENT] Typing improvements. [#​935](https://redirect.github.com/prometheus/client_python/issues/935), [#​970](https://redirect.github.com/prometheus/client_python/issues/970) \[ENHANCEMENT] Allow enabling or disabling `_created` metrics from code. [#​973](https://redirect.github.com/prometheus/client_python/issues/973) \[BUGFIX] Change #!/usr/bin/python to #!/usr/bin/env python in remaining places. [#​945](https://redirect.github.com/prometheus/client_python/issues/945) ### [`v0.17.1`](https://redirect.github.com/prometheus/client_python/releases/tag/v0.17.1): 0.17.1 / 2023-07-19 [Compare Source](https://redirect.github.com/prometheus/client_python/compare/v0.17.0...v0.17.1) \[BUGFIX] Use #!/usr/bin/env python instead of #!usr/bin/python in bridge/graphite.py. [#​928](https://redirect.github.com/prometheus/client_python/issues/928)

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