The error was:
```
Jobs::Onceoff can run all once off jobs without errors
Failure/Error: j.new.execute_onceoff(nil)
TypeError:
can't create instance of singleton class
# ./spec/integrity/onceoff_integrity_spec.rb:13:in `new'
# ./spec/integrity/onceoff_integrity_spec.rb:13:in `block (3 levels) in <main>'
# ./spec/integrity/onceoff_integrity_spec.rb:12:in `each'
# ./spec/integrity/onceoff_integrity_spec.rb:12:in `block (2 levels) in <main>'
# ./spec/rails_helper.rb:279:in `block (2 levels) in <top (required)>'
# ./bundle/ruby/2.7.0/gems/webmock-3.13.0/lib/webmock/rspec.rb:37:in `block (2 levels) in <top (required)>'
```
Sometimes the class found by `ObjectSpace.each_object(Class)` would be e.g:
`#<Class:#<Jobs::MigrateBadgeImageToUploads:0x00007f96f8277400>>`
…instead of e.g:
`#<Jobs::MigrateBadgeImageToUploads:0x00007f96ffa59540>`
This commit changes the `#select` to filter out those classes.
7dab169990