Prepare the FabricBot config for migration to Policy Service

[jeffhandley]

This updates the FabricBot configuration to address issues we've seen migrating other repositories to the Policy Service automation. There is one behavioral change with a loss of functionality.

1. Remove the auto-merge automation
   • This automation configuration was relying on some rich features of the FabricBot's own auto-merge functionality
   • That functionality was in place before GitHub's own auto-merge functionality
   • Because GitHub has built-in auto-merge capabilities, the Policy Service does not provide its own implementation
   • Policy Service does have automation that allows for a PR to have auto-merge enabled or disabled, but it can't rely on the types of conditions used here
   • The result is there is not a way to port this configuration forward, and a different approach is needed
   • The recommendation is to investigate Arcade-based auto-merge behaviors or implementing a GitHub Action
2. Explicitly add a filter for isIssue or isPr where that was previously implied
   • There was a task configured for `"eventType" that when ported to Policy Service, this implicit filter will be lost
   • This updates the config to explicitly add that filter so behavior stays the same after the migration
3. Remove references to project automation (it was superfluous)

/cc @mkArtakMSFT @wtgodbe @JohannesLampel

[sharwell]

I have no objection to this change, but I don't know enough about Fabric Bot to understand the correctness of the change. Hopefully I can get all these rules converted to Github Actions in time to make the conversion to policy service unnecessary/irrelevant.