remove `pattern` property support in ruby files

[BBBmau]

Since we've removed the use of pattern field in all yaml files, we also need to remove support for pattern in ruby. This is found in types.erb and yaml_conversion_fields.erb

This PR will be merged once a soak period of 2 weeks passes.

Fixes https://github.com/hashicorp/terraform-provider-google/issues/17269

Release Note Template for Downstream PRs (will be copied)

[BBBmau]

/gcbrun

[rileykarson]

Hey! I'm closing this PR as a part of a cleanup of older inactive PRs, using a threshold of PRs last updated over 3 months ago. This doesn't represent rejection of the change, and feel free to comment for me to reopen it if you plan to pick it back up, or feel free to start a new PR with the same changes in the future.