Changelog entry files must have a .txt extension

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/fix_cmake_gen_files b/ChangeLog.d/fix_cmake_gen_files.txt
similarity index 100%
rename from ChangeLog.d/fix_cmake_gen_files
rename to ChangeLog.d/fix_cmake_gen_files.txt
diff --git a/ChangeLog.d/fix_hard_link_across_drives b/ChangeLog.d/fix_hard_link_across_drives.txt
similarity index 100%
rename from ChangeLog.d/fix_hard_link_across_drives
rename to ChangeLog.d/fix_hard_link_across_drives.txt