clean: remove unnecessary variable

clean: remove unnecessary variable

The variable `matches` used to hold the return of a `dir_path_match()`
call that was removed in 95c11ecc73 ("Fix error-prone fill_directory()
API; make it only return matches", 2020-04-01). Now `matches` will
always hold 0, which is the value it's initialized with; and the
condition `matches != MATCHED_EXACTLY` will always evaluate to true. So
let's remove this unnecessary variable.

Interestingly, it seems that `matches != MATCHED_EXACTLY` was already
unnecessary before 95c11ecc73. That's because `remove_directories` is
always set to 1 when we have pathspecs; So, in the condition
`!remove_directories && matches != MATCHED_EXACTLY`, we would either:

- have pathspecs (or have been given `-d`) and ignore `matches` because
  `remove_directories` is 1; or

- not have pathspecs (nor `-d`) and end up just checking that
  `0 != MATCHED_EXACTLY`, as `matches` would never get reassigned
  after its zero initialization (because there is no pathspec to match).

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>