chore: bump go version to 1.22

[s4kh]

What this PR does / why we need it: Dropping support for 1.21 to allow otel dependency updates (which dropped support for Go 1.21), see https://github.com/grafana/grafana-plugin-sdk-go/pull/1092, https://github.com/grafana/grafana-plugin-sdk-go/pull/1086, https://github.com/grafana/grafana-plugin-sdk-go/pull/1084 and https://github.com/grafana/grafana-plugin-sdk-go/pull/1083

Which issue(s) this PR fixes:

Part of https://github.com/grafana/grafana-plugin-sdk-go/issues/1107

Special notes for your reviewer:

[CLAassistant]

All committers have signed the CLA.

[github-actions[bot]]

Hello! 👋 This repository uses Auto for releasing packages using PR labels.

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[marefr]

You might want to check with the team if this should trigger a release (I think so)

[grafana-plugins-platform-bot[bot]]

:rocket: PR was released in @grafana/create-plugin@5.6.0, @grafana/plugin-e2e@1.9.0 :rocket: