Part 2: Remove unnecessary allows between gitlab_schemas

What does this MR do and why?

gitlab_main_clusterwide and gitlab_main_cell will continue to be on the same database main for each cell. We have re-allowed cross-joins and cross database modifications for tables for both of these gitlab_schemas. So all the exception allow-listing on tables are not necessary anymore.

This MR is part 2. To avoid changing so many tables within each MR.

Part 1: !153294 (merged)

Script used to create this change

1. Created a Ruby script called modify.rb (first name came to my mind)

require 'yaml'

content = YAML.load(File.read(ARGV[0]))

if content["allow_cross_joins"] || content["allow_cross_transactions"]
  content.delete("allow_cross_joins")
  content.delete("allow_cross_transactions")

  f = File.open(ARGV[0], 'w')
    f.write(YAML.dump(content, indentation: 0, line_width: 120))
  f.close
end

2. cd db/docs
3. for f in *.yml; do ruby modify.rb $f; done

MR acceptance checklist

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