[Azure Pipelines] drop old workaround for safaridriver --version (#18454)

The `--version` argument is supported starting in Safari 12.1:
web-platform-tests/results-collection#617

Author: foolip

.azure-pipelines.yml

@@ -334,10 +334,7 @@ jobs:
       channel: stable
   - template: tools/ci/azure/update_hosts.yml
   - template: tools/ci/azure/update_manifest.yml
-  - script: |
-      # TODO: drop this when `safaridriver --version` is supported.
-      SAFARI_VERSION="$(/usr/libexec/PlistBuddy -c 'Print :CFBundleShortVersionString' /Applications/Safari.app/Contents/Info.plist) ($(/usr/libexec/PlistBuddy -c 'Print :CFBundleVersion' /Applications/Safari.app/Contents/Info.plist))"
-      no_proxy='*' ./wpt run --no-manifest-update --no-restart-on-unexpected --no-fail-on-unexpected --this-chunk=$(System.JobPositionInPhase) --total-chunks=$(System.TotalJobsInPhase) --chunk-type hash --log-wptreport $(Build.ArtifactStagingDirectory)/wpt_report_$(System.JobPositionInPhase).json --log-wptscreenshot $(Build.ArtifactStagingDirectory)/wpt_screenshot_$(System.JobPositionInPhase).txt --log-tbpl - --log-tbpl-level info --browser-version "$SAFARI_VERSION" safari
+  - script: no_proxy='*' ./wpt run --no-manifest-update --no-restart-on-unexpected --no-fail-on-unexpected --this-chunk=$(System.JobPositionInPhase) --total-chunks=$(System.TotalJobsInPhase) --chunk-type hash --log-wptreport $(Build.ArtifactStagingDirectory)/wpt_report_$(System.JobPositionInPhase).json --log-wptscreenshot $(Build.ArtifactStagingDirectory)/wpt_screenshot_$(System.JobPositionInPhase).txt --log-tbpl - --log-tbpl-level info safari
     displayName: 'Run tests'
   - task: PublishBuildArtifacts@1
     displayName: 'Publish results'