Bump github.com/prometheus/common from 0.15.0 to 0.21.0

[dependabot-preview[bot]]

Bumps github.com/prometheus/common from 0.15.0 to 0.21.0.

Release notes

Sourced from github.com/prometheus/common's releases.

v0.19.0

Add JSON marshalling to durations.

v0.18.0

Support follow_redirects

v0.17.0

Remove private fields in http client #274

v0.16.0

• Make Duration implement encoding.TextUnmarshaler #270
• Support authorization credentials (replaces bearer_token) #272

Commits

• 3b362f5 Merge pull request #291 from pracucci/add-custom-dialer-option-to-http-client
• 6a9c79c Move HTTP keepalive and HTTP2 options to functional options
• 50bd6ae Added functional option to allow to customize DialContext() in HTTP client
• 4240322 Validate duration overflow
• 6e540be Merge pull request #283 from lupine/patch-1
• 112a9d4 Stop testing against go1.9-1.12
• c1bba9e Generate hashCAFile with SHA256
• 3ebd397 Merge pull request #280 from 56quarters/duration-json
• 745afa4 Code review feedback
• 2a23014 Add methods to model.Duration for JSON marshalling and unmarshalling
• Additional commits viewable in compare view

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[dependabot-preview[bot]]

Superseded by #219.