Cleanup unnecessary file modifications in t1400-update-ref

Kristian Høgsberg pointed out that the two file modifications
we were doing during the 'creating initial files' step are not even
used within the test suite.  This was actually confusing as we do
not even need these changes for the tests to pass.  All that really
matters here is the specific commit dates are used so that these
appear in the branch's reflog, and that the dates are different so
that the branch will update when asked and the reflog entry is
also updated.  There is no need for the file modification.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t1400-update-ref.sh

@@ -198,11 +198,9 @@ test_expect_success \
 	 GIT_AUTHOR_DATE="2005-05-26 23:41" \
 	 GIT_COMMITTER_DATE="2005-05-26 23:41" git-commit -F M -a &&
 	 h_OTHER=$(git rev-parse --verify HEAD) &&
-	 echo FIXED >F &&
 	 GIT_AUTHOR_DATE="2005-05-26 23:44" \
 	 GIT_COMMITTER_DATE="2005-05-26 23:44" git-commit --amend &&
 	 h_FIXED=$(git rev-parse --verify HEAD) &&
-	 echo TEST+FIXED >F &&
 	 echo Merged initial commit and a later commit. >M &&
 	 echo $h_TEST >.git/MERGE_HEAD &&
 	 GIT_AUTHOR_DATE="2005-05-26 23:45" \