Consider removing workspaceContains activation event

[TylerLeonhardt]

Is your feature request related to a problem? Please describe.

This extension will eagerly activate if I have any workflow files in my repo... even if I don't intend to do any work on GitHub Actions in my repo.

This is because this extension has the following activation event:
https://github.com/github/vscode-github-actions/blob/main/package.json#L28

Describe the solution you'd like

Remove this activation event. Your extension will already activate when one of your views open or when you open a workflow file thanks to your registering of a language. This should be sufficient. If it's not, I'm curious to know why.

Additional context

Activating eagerly affects other extensions running in the extension host and the ideal situation is that only extensions that are absolutely needed are activated. This keeps VS Code & the extension host lean and fast.