t5516: fix test order flakiness

The 'fetch follows tags by default' test sorts using 'sort -k 4', but
for-each-ref output only has 3 columns. This relies on sort treating
records with fewer fields as having an empty fourth field, which may
produce unstable results depending on locale. Use 'sort -k 3' to match
the actual number of columns in the output.

Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

t/t5516-fetch-push.sh

@@ -1349,7 +1349,7 @@ test_expect_success 'fetch follows tags by default' '
 		git for-each-ref >tmp1 &&
 		sed -n "p; s|refs/heads/main$|refs/remotes/origin/main|p" tmp1 |
 		sed -n "p; s|refs/heads/main$|refs/remotes/origin/HEAD|p"  |
-		sort -k 4 >../expect
+		sort -k 3 >../expect
 	) &&
 	test_when_finished "rm -rf dst" &&
 	git init dst &&