SQUASH??? fixup

The test as posted breaks when run with

    $ make WITH_BREAKING_CHANGES=YesPlease test

as the added part assumes that the default branch name is "master".

This band-aid is sufficient for the purpose of the maintainer to get
the CI passing, but the real solution should probably be done better
in such a way that the latter step does not have to rely on the
creation of "anchorpoint" in the previous step.  I'll leave it to
the contributor of the topic.

Author: gitster

t/t5572-pull-submodule.sh

@@ -246,7 +246,8 @@ test_expect_success 'fetch submodule remote of different name from superproject'
 	git -C child submodule update --init &&
 
 	# Needs to create unreachable commit from current master branch.
-	git -C a-submodule checkout -b newmain HEAD^ &&
+	git -C a-submodule tag anchorpoint HEAD &&
+	git -C a-submodule checkout -b newmain anchorpoint^ &&
 	test_commit -C a-submodule echo &&
 	test_commit -C a-submodule moreecho &&
 	subc=$(git -C a-submodule rev-parse --short HEAD) &&
@@ -265,7 +266,7 @@ test_expect_success 'fetch submodule remote of different non-origin name from su
 	git -C child/a-submodule remote rename origin o2 &&
 
 	# Create commit that is unreachable from current master branch
-	git -C a-submodule checkout -b newmain2 master^ &&
+	git -C a-submodule checkout -b newmain2 anchorpoint^ &&
 	test_commit -C a-submodule echo_o2 &&
 	test_commit -C a-submodule moreecho_o2 &&
 	subc=$(git -C a-submodule rev-parse --short HEAD) &&