Simplifies commit message validation to the simplest possible logic: a
straightforward regex on the PR title.
### Testing
* (Note: the testing procedure below is based on v6.0, not v5.0;
however, the logic at play will apply regardless of v5.0 vs v6.0)
* I spawned a new "parent" branch from `v6.0`:
(`stevegrossmongodb-v6.0-mq`)
* I established GitHub configuration and Evergreen project to match what
is used in v6.0.
* I created [this PR](https://github.com/10gen/mongo/pull/22012) to test
changes to the message validation logic.
* I ran this [PB for a commit with an invalid
title](https://spruce.mongodb.com/task/stevegrossmongodb_v6.0_mq_commit_queue_validate_commit_message_patch_834c3296202453d3e555b76f06e91eb505ebf006_663b98b0e2c04200074f34a4_24_05_08_15_22_29/logs?execution=0&logtype=all),
which correct failed
* I ran this [PB for commit with a valid
title](https://evergreen.mongodb.com/version/663b9f0b1542760007b768d2?redirect_spruce_users=true),
which correctly passed
* I ran the unit tests for validate_commit_message.py:
```
> python -m unittest buildscripts.tests.test_validate_commit_message
Found a commit without a ticket
SERVER-
Found a commit without a ticket
Revert SERVER-60
Found a commit without a ticket
Found a commit without a ticket
nonsense
.Must specify non-empty value for --message
..
----------------------------------------------------------------------
Ran 3 tests in 0.003s
OK
```
GitOrigin-RevId: ec0b8cfc4a6433b1ad4572e1b910e6ad71ee36fd
stevegrossmongodb
Juan Gu
David Bradford
Lydia Stepanek
Jim OLeary
Jim O'Leary