[llvm] [DOCS][BUILDBOT] Bump recommended worker version (PR #144853)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

Hey @DavidSpickett,

Thanks for your review. 

> I know that the version used for the server right now is not the latest. Need to be sure it's compatible.

Yes, what you suggest sounds right to me.

To add a bit more context, I had a brief discussion with @gkistanova before opening the PR,
and there was no recollection of any issues with recent versions of `buildbot-worker`.

So I went ahead and updated the version to match the one suggested in the local configuration.
That said, I'm open to changing both places again, if we think a different recent version would be appropriate.

https://github.com/llvm/llvm-project/pull/144853