typing: fix the signature of `treemanifest.fastdelta()`
We're still missing a few explicit bits of Protocol subclassing, and pytype
found this when the subclassing is applied. So fix this first.
--- a/mercurial/manifest.py Wed Feb 19 23:18:17 2025 +0100
+++ b/mercurial/manifest.py Tue Dec 17 19:29:08 2024 -0500
@@ -1345,7 +1345,7 @@
def fastdelta(
self, base: ByteString, changes: Iterable[Tuple[bytes, bool]]
- ) -> ByteString:
+ ) -> tuple[ByteString, ByteString]:
raise FastdeltaUnavailable()
def diff(