rhg: in path_encode, be a bit more conservative about memory usage Use [shrink_to_fit] to match the previous behavior more closely, and potentially save (a tiny bit) of memory. FWIW, I suspect this is unnecessary, but this whole MR is about simplifying things while preserving any existing optimizations.

--- a/rust/hg-core/src/revlog/path_encode.rs	Thu Feb 16 19:14:51 2023 +0000
+++ b/rust/hg-core/src/revlog/path_encode.rs	Fri Feb 17 13:29:39 2023 +0000
@@ -576,6 +576,7 @@
     if let Some(l) = last_dot {
         dest.write_bytes(&src[l..]);
     }
+    dest.shrink_to_fit();
     dest
 }