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

[David Blaikie via cfe-commits]

dwblaikie wrote:

+1 to @pogo59's comment about pruning complete paths - I suspect they're in the minority. Might be worth checking whether the `===` at the start and end is markup for any particular thing (I /think/ the `-*- C++ -*-` is load bearing for some editors to inform them this `.h` file is C++ not C, so I'm not sure about some other features of those top-of-file comments).

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