Clean up pg_query gem native extension directory

This removes a 30 MB directory that contains the lib_pgquery source and
compiled objects. These files are not needed for the pg_query gem to
work.

Closes https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5747

changelogs/unreleased/sh-cleanup-pgquery-ext.yml

+---
+title: Clean up pg_query gem native extension directory
+merge_request: 4683
+author:
+type: other

config/projects/gitlab.rb

@@ -222,6 +222,7 @@ exclude 'embedded/lib/ruby/gems/*/gems/grpc-*/src/ruby/spec'
 exclude 'embedded/lib/ruby/gems/*/gems/grpc-*/third_party'
 exclude 'embedded/lib/ruby/gems/*/gems/rbtrace-*/ext/src'
 exclude 'embedded/lib/ruby/gems/*/gems/rbtrace-*/ext/dst'
+exclude 'embedded/lib/ruby/gems/*/gems/*pg_query-*/ext'
 # Enable signing packages
 package :rpm do