workflow: enable cockroach-microbench-ci for pull requests

`cockroach-microbench-ci` was disabled due to being noisy
#129390. After analysis of
the runs, it was deduced that the variance each run is quite high. This
required increasing the threshold and in this PR it is being increased
to 20%.

Epic: none

Release note: None

.github/workflows/github-actions-essential-ci.yml

@@ -347,8 +347,6 @@ jobs:
         if: always()
   cockroach-microbench-ci:
     runs-on: [ self-hosted, basic_runner_group ]
-    # TODO(sambhav-jain-16): enable this for pull requests also
-    if: ${{ github.event_name == 'push' }}
     timeout-minutes: 60
     steps:
       - uses: actions/checkout@v4
@@ -383,7 +381,7 @@ jobs:
       - name: run scripts
         run: ./build/github/cockroach-microbench-ci.sh
         env:
-          COMPARE_THRESHOLD: "5.00"
+          COMPARE_THRESHOLD: "20.00"
           PUSH_STEP: ${{ github.event_name == 'push' && env.GITHUB_ACTIONS_BRANCH != 'staging' }}
           BASE_SHA: ${{ steps.get_latest_commit_target_branch.outputs.latest_commit }}