Adjust mocha .only check

[selfcontained]

Description

Had some false positives with the existing .only check (would fail for any changes that included the word only. I've adjust the regex to match a bit more precisely.

Related Issue(s)

Fixes #

How to test

If the build passes then it should be a decent test, as the line change in this PR includes the words only, which would have failed it previously.

Release Notes

NONE

Documentation

Build Options:

• /werft with-werft
  Run the build with werft instead of GHA
• leeway-no-cache
• /werft no-test
  Run Leeway with --dont-test

Publish Options

• /werft publish-to-npm
• /werft publish-to-jb-marketplace

Installer Options

• with-dedicated-emulation
• with-ws-manager-mk2
• workspace-feature-flags
  Add desired feature flags to the end of the line above, space separated

Preview Environment Options:

• /werft with-local-preview
  If enabled this will build install/preview
• /werft with-preview
• /werft with-large-vm
• /werft with-gce-vm
  If enabled this will create the environment on GCE infra
• with-integration-tests=all
  Valid options are all, workspace, webapp, ide, jetbrains, vscode, ssh