Fix typo in README (#11)

Author: muzimuzhi

README.md

@@ -198,7 +198,7 @@ Changes
   - Update data files to Unicode release 15.0.0
 - v1.17 (2023-09-18)
   - Update data files to Unicode release 15.1.0
-  - Adjust `load-unicode-xetex-classes.txt` for modified data file format
+  - Adjust `load-unicode-xetex-classes.tex` for modified data file format
 - v1.18 (2025-01-07)
   - Update data files to Unicode release 16.0.0