correct filename for jobs tests
Remove defunct ivars

@column_names_with_alias, @dynamic_methods_hash, @time_zone_column_names, and @cached_time_zone
Merge pull request #17092 from Empact/defunct-ivars

Remove defunct ivars
Use Hash#each_key instead of Hash#keys.each

Hash#keys.each allocates an array of keys; Hash#each_key iterates through the
keys without allocating a new array. This is the reason why Hash#each_key
exists.
Merge pull request #17086 from seuros/master

correct filename for jobs tests
Merge pull request #17099 from sferik/each_key

Use Hash#each_key instead of Hash#keys.each