[llvm] [workflow] Don't add a comment when the first run of the formatter passes (PR #86335)

[Tom Stellard via llvm-commits]

tstellar wrote:

> What are the advantages of the second option? Just producing an empty JSON file seems like the simplest solution to me.

It turns out there is no way to implement the 2nd option anyway, so I just went with the empty JSON.  

https://github.com/llvm/llvm-project/pull/86335