Fix version checking in mimirtool

[dimitarvdimitrov]

Signed-off-by: Dimitar Dimitrov dimitar.dimitrov@grafana.com

What this PR does

Fixes a bug where version checking was broken

$ mimirtool version
Mimirtool, version 2.2.0 (branch: HEAD, revision: 65344e2ed)
  go version:       go1.17.8
  platform:         darwin/arm64
checking latest version... A newer version of mimirtool is available, please update to mimir-2.2.0

Also adds a link to the release

$ cmd/mimirtool/mimirtool version
Mimirtool, version 2.3.0 (branch: dimitar/fix-mimirtool-version-check, revision: 64c5aefa8)
  go version:       go1.18.4
  platform:         darwin/arm64
checking latest version... A newer version of mimirtool is available, please update to 2.2.0 https://github.com/grafana/mimir/releases/tag/mimir-2.2.0

Which issue(s) this PR fixes or relates to

Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[krajorama]

LGTM, reproduced error, could not check fix because version is uknown in unreleased version