[tooling][gitlab] automatically trigger release candidate workflow

[celenechang]

What does this PR do?

Automatically trigger release candidate workflow for tag pipelines

It was initially set to require a manual trigger so it could be tested

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

Describe your test plan

Write there any instructions and details you may have to test your PR.

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.86%. Comparing base (54f43d1) to head (185e9fe).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1521   +/-   ##
=======================================
  Coverage   48.86%   48.86%           
=======================================
  Files         225      225           
  Lines       19959    19959           
=======================================
  Hits         9753     9753           
  Misses       9695     9695           
  Partials      511      511           

Flag	Coverage Δ
unittests	48.86% <ø> (ø)

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