[GHF] Add spaces between words in merge fail reasons (#78378)
I.e. reviewers name should be comma+space separator as well as failed job named should be space separate from colon before that
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78378
Approved by: https://github.com/suo, https://github.com/atalman, https://github.com/janeyx99
