test-lib-functions: remove test_subcommand_inexact

test-lib-functions: remove test_subcommand_inexact

The implementation of test_subcommand_inexact() was originally
introduced in e4d0c11c0 (repack: respect kept objects with '--write-midx
-b', 2021-12-20) with the intention to allow finding a subcommand based
on an initial set of arguments. The inexactness was intended as a way to
allow flexible options beyond that initial set, as opposed to
test_subcommand() which requires that the full list of options is
provided in its entirety.

The implementation began by copying test_subcommand() and replaced the
repeated argument 'printf' statement to append ".*" instead of "," to
each argument. This caused it to be more flexible than initially
intended.

The previous change deleted the only use of test_subcommand_inexact, so
instead of editing the helper, delete it.

Helped-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>