[NFC][clang]Increase the number of driver diagnostics

We're close to hitting the limited number of driver diagnostics, increase `DIAG_SIZE_DRIVER` to accommodate more.

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D114615

GitOrigin-RevId: 3c32c568844c745e3fe7fa72ce3aa65340e545bc
1 file changed