[llvm] [Github] Fetch all commits in PR for code formatting checks (PR #69766)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

Weird that the sparse checkout was slow in your previous experience. I'll definitely make sure to keep an eye out for weird failures. There's gotta be at least something. I'll keep an eye on the timing for the sparse checkouts and make sure nothing blows up there too.

I'll let @tstellar take a look to make sure I'm not doing anything too crazy, update the PR message, and then merge.

https://github.com/llvm/llvm-project/pull/69766