Fixes:
```
Version.joins(dependencies: :rubygem).where(rubygems: { name: "rails" })
Traceback (most recent call last):
ActiveRecord::StatementInvalid (PG::UndefinedTable: ERROR:  invalid
reference to FROM-clause entry for table "rubygems")
LINE 1: ...dencies"."id" = "dependencies"."rubygem_id" WHERE
"rubygems"...
                                                             ^
HINT:  Perhaps you meant to reference the table alias
"rubygems_dependencies".
```

fix for yarn file missing is no longer needed.
versions_test.rb was updated to fix:
```
DEPRECATION WARNING: ActiveModel::Errors#keys is deprecated and will be
removed in Rails 6.2.

To achieve the same use:

  errors.attribute_names (called from block in <class:VersionTest> at
/home/aditya/rubygems.org/test/unit/version_test.rb:886)
```