t5411: adjust the remaining support files for init.defaultBranch=main

t5411: adjust the remaining support files for init.defaultBranch=main

This trick was performed via

	$ sed -i -e 's/master/main/g' -e 's/MASTER/MAIN/g' \
		-e 's/Master/Main/g' -- t/t5411/*

In the previous commit, we adjusted roughly half of the support files,
to stay under the 100kB limit (mails larger than that are rejected by
the Git mailing list).

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