[clang] [clang][NFC] Trim license header comments to 81 characters (PR #82919)

[Paul T Robinson via cfe-commits]

pogo59 wrote:

I grepped `clang` for "^/+=[^/]*/.*\.(h|cpp) " and found only 35 files with directory components. So, the majority of files have only the filename in the header line. The example in the Coding Standard does not reflect common practice.

I think it's fine to remove everything but the filename.

https://github.com/llvm/llvm-project/pull/82919