chore(deps): update actions/cache action to v2.1.6

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/cache	action	minor	v2 -> v2.1.6

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Release Notes

actions/cache

### [`v2.1.6`](https://togithub.com/actions/cache/releases/v2.1.6) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.5...v2.1.6) - Catch unhandled "bad file descriptor" errors that sometimes occurs when the cache server returns non-successful response (https://github.com/actions/cache/pull/596) ### [`v2.1.5`](https://togithub.com/actions/cache/releases/v2.1.5) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.4...v2.1.5) - Fix permissions error seen when extracting caches with GNU tar that were previously created using BSD tar (https://github.com/actions/cache/issues/527) ### [`v2.1.4`](https://togithub.com/actions/cache/releases/v2.1.4) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.3...v2.1.4) - Make caching more verbose [#​650](https://togithub.com/actions/toolkit/pull/650) - Use GNU tar on macOS if available [#​701](https://togithub.com/actions/toolkit/pull/701) ### [`v2.1.3`](https://togithub.com/actions/cache/releases/v2.1.3) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.2...v2.1.3) - Upgrades `@actions/core` to v1.2.6 for [CVE-2020-15228](https://togithub.com/advisories/GHSA-mfwh-5m23-j46w). This action was not using the affected methods. - Fix error handling in `uploadChunk` where 400-level errors were not being detected and handled correctly ### [`v2.1.2`](https://togithub.com/actions/cache/releases/v2.1.2) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.1...v2.1.2) - Adds input to limit the chunk upload size, useful for self-hosted runners with slower upload speeds - No-op when executing on GHES ### [`v2.1.1`](https://togithub.com/actions/cache/releases/v2.1.1) [Compare Source](https://togithub.com/actions/cache/compare/v2.1.0...v2.1.1) - Update `@actions/cache` package to `v1.0.2` which allows cache action to use posix format when taring files. ### [`v2.1.0`](https://togithub.com/actions/cache/releases/v2.1.0) [Compare Source](https://togithub.com/actions/cache/compare/v2.0.0...v2.1.0) - Replaces the `http-client` with the Azure Storage SDK for NodeJS when downloading cache content from Azure. This should help improve download performance and reliability as the SDK downloads files in 4 MB chunks, which can be parallelized and retried independently - Display download progress and speed

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