Relax the subject line requirements for commits

What does this MR do?

This changes the hard limit of 50 to a soft limit of 50, with the new hard limit being 72 characters. This gives people a bit more space, while still (hopefully) guiding them towards subject lines that are roughly 50 characters long.

Example of the new setup:

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/release/framework/issues/16

Does this MR meet the acceptance criteria?

• Conforms to the code review guidelines
• Conforms to the style guides
• Conforms to the database guides