ci: pare down unit tests (#824)

Author: jackwotherspoon

.github/workflows/tests.yml

@@ -149,11 +149,10 @@ jobs:
     # run job on proper workflow event triggers (skip job for pull_request event from forks and only run pull_request_target for "tests: run" label)  
     if: "${{ (github.event.action != 'labeled' && github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name) || github.event.label.name == 'tests: run' }}"
     name: unit tests
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
     strategy:
       matrix:
-        os: [macos-latest, windows-latest, ubuntu-latest]
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.11"]
       fail-fast: false
     permissions:
       contents: read
@@ -212,16 +211,4 @@ jobs:
           curl https://github.com/googleapis/repo-automation-bots/releases/download/flakybot-1.1.0/flakybot -o flakybot -s -L
           chmod +x ./flakybot
           ./flakybot --repo ${{github.repository}} --commit_hash ${{github.sha}} --build_url https://github.com/${{github.repository}}/actions/runs/${{github.run_id}}
-      - name: FlakyBot (Windows)
-        # only run flakybot on periodic (schedule) and continuous (push) events
-        if: ${{ (github.event_name == 'schedule' || github.event_name == 'push') && runner.os == 'Windows' && always() }}
-        run: |
-          curl https://github.com/googleapis/repo-automation-bots/releases/download/flakybot-1.1.0/flakybot.exe -o flakybot.exe -s -L
-          ./flakybot.exe --repo ${{github.repository}} --commit_hash ${{github.sha}} --build_url https://github.com/${{github.repository}}/actions/runs/${{github.run_id}}
-      - name: FlakyBot (macOS)
-        # only run flakybot on periodic (schedule) and continuous (push) events
-        if: ${{ (github.event_name == 'schedule' || github.event_name == 'push') && runner.os == 'macOS' && always() }}
-        run: |
-          curl https://github.com/googleapis/repo-automation-bots/releases/download/flakybot-1.1.0/flakybot-darwin-amd64 -o flakybot -s -L
-          chmod +x ./flakybot
-          ./flakybot --repo ${{github.repository}} --commit_hash ${{github.sha}} --build_url https://github.com/${{github.repository}}/actions/runs/${{github.run_id}}
+