t/pack-refs-tests: drop '-f' from test_path_is_missing

test_path_is_missing expects exactly one argument: the path to
check for absence. Passing '-f' is incorrect and results in
"bug in the test script: 1 param" during test execution.

The '-f' flag appears to have been carried over from the
equivalent 'test -f' usage, but test_path_is_missing does not
accept such flags.

Remove the extraneous '-f' to use the helper correctly and
restore proper test behavior.

Signed-off-by: Jayesh Daga <jayeshdaga99@gmail.com>

Author: jayesh0104

t/pack-refs-tests.sh

@@ -1,9 +1,3 @@
-#!/bin/sh
-
-test_description='test pack-refs'
-
-. ./test-lib.sh
-
 pack_refs=${pack_refs:-pack-refs}
 
 test_expect_success 'enable reflogs' '