[clang] [clang-tools-extra] [lldb] [llvm] [mlir] [NFC] Fix typos 'seperate' -> 'separate' (PR #144368)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Please change your email settings as explained in https://llvm.org/docs/DeveloperPolicy.html#email-addresses. Right now it would be merged with a GitHub noreply address.

https://github.com/llvm/llvm-project/pull/144368