[Mlir-commits] [mlir] [mlir-lsp] Rename `OutgoingNotification` (PR #90076)

[River Riddle]

https://github.com/River707 approved this pull request.

Typedefs are fairly cheap, so it isn't really that necessary to share here, but the code still reads fine after this change, so LGTM. Could you split out the new test from the rename? Can be done when landing.

https://github.com/llvm/llvm-project/pull/90076