t/t7003: replace \t with literal tab in sed expression

The sed utilities on IRIX and Solaris do not interpret the sequence '\t'
to mean a tab character;  they read a literal character 't'.  So, use a
literal tab instead.
Signed-off-by: NBrandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t7003-filter-branch.sh

@@ -143,7 +143,7 @@ test_expect_success 'more setup' '
 test_expect_success 'use index-filter to move into a subdirectory' '
 	git branch directorymoved &&
 	git filter-branch -f --index-filter \
-		 "git ls-files -s | sed \"s-\\t-&newsubdir/-\" |
+		 "git ls-files -s | sed \"s-	-&newsubdir/-\" |
 	          GIT_INDEX_FILE=\$GIT_INDEX_FILE.new \
 			git update-index --index-info &&
 		  mv \"\$GIT_INDEX_FILE.new\" \"\$GIT_INDEX_FILE\"" directorymoved &&