Revert "Add a helper function to compare file contents"

Revert "Add a helper function to compare file contents"

Now that during a `git clone`, the hooks' contents are no longer
compared to the templates' files', the caller for which the
`do_files_match()` function was introduced is gone, and therefore this
function can be retired, too.

This reverts commit 584de0b4c23 (Add a helper function to compare file
contents, 2024-03-30).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>