Remove one of the last remaining uses of
"TEST_GIT_DEFAULT_INITIAL_BRANCH= main" in the test suite. We have
been steadily be converting tests from using "master" as the default
branch name since the introduction of TEST_GIT_DEFAULT_INITIAL_BRANCH
in 704fed9ea2 (tests: start moving to a different default main branch
name, 2020-10-23) The changes here are purely mechanical replacing
"master" with "main"
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Phillip Wood