lsp: Skip computation of `edits_since_save` when there are no disk based diagnostics (#23269)

Thought of this improvement while @ConradIrwin and I were looking into
whether this code is misbehaving. It seems not to be.

Release Notes:

- N/A
10f358633bMichael Sloan committed on 1/18/2025, 8:28:44 PM· committed by GitHubparent9a7b73b
1 file changedLine totals unavailable