t3020: fix typo in test description

Signed-off-by: NSZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t3020-ls-files-error-unmatch.sh

@@ -20,7 +20,7 @@ test_expect_failure \
     'git ls-files --error-unmatch foo bar-does-not-match'
 
 test_expect_success \
-    'git ls-files --error-unmatch should succeed eith matched paths.' \
+    'git ls-files --error-unmatch should succeed with matched paths.' \
     'git ls-files --error-unmatch foo bar'
 
 test_done