ci: update regression check rules for release tags

[brettlangdon]

Fix for #13135 which incorrectly was looking at the branch name and not the tag name.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

.gitlab/benchmarks/microbenchmarks.yml                                  @DataDog/python-guild @DataDog/apm-core-python

[github-actions]

The backport to 2.21 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.21 2.21
# Navigate to the new working tree
cd .worktrees/backport-2.21
# Create a new branch
git switch --create backport-13141-to-2.21
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 1871f28c49426e6a1ad2880adfb1e558f139b5bc
# Push it to GitHub
git push --set-upstream origin backport-13141-to-2.21
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.21

Then, create a pull request where the base branch is 2.21 and the compare/head branch is backport-13141-to-2.21.

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 232 ± 3 ms.

The average import time from base is: 232 ± 2 ms.

The import time difference between this PR and base is: 0.5 ± 0.1 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.792 ms (0.77%)

ddtrace.bootstrap.sitecustomize 1.133 ms (0.49%)

ddtrace.bootstrap.preload 1.133 ms (0.49%)

ddtrace.internal.products 1.133 ms (0.49%)

ddtrace.internal.remoteconfig.client 0.579 ms (0.25%)

ddtrace 0.659 ms (0.28%)