Update 1.6.4 changelog entry.

The previous looked to be a copy/paste from the previous one.

Author: ehuss

libgit2-sys/CHANGELOG.md

@@ -6,8 +6,7 @@
 ### Changed
 
 - Updated to libgit2 [1.6.4](https://github.com/libgit2/libgit2/releases/tag/v1.6.4).
-  This brings in many changes, including better SSH host key support on Windows and better SSH host key algorithm negotiation.
-  1.6.3 is now the minimum supported version.
+  This brings in a minor fix on Windows when the ProgramData directory does not exist.
   [#948](https://github.com/rust-lang/git2-rs/pull/948)
 
 ## 0.15.0+1.6.3 - 2023-04-02