Remove test which fails with Go >= 1.15 due to API changes.
This patch should no longer be necessary with doublestar v4+

diff --git a/doublestar_test.go b/doublestar_test.go
index b21d20ad4b..f510c3d06b 100644
--- a/doublestar_test.go
+++ b/doublestar_test.go
@@ -80,7 +80,6 @@ var matchTests = []MatchTest{
 	{"[", "a", false, ErrBadPattern, true},
 	{"[^", "a", false, ErrBadPattern, true},
 	{"[^bc", "a", false, ErrBadPattern, true},
-	{"a[", "a", false, nil, false},
 	{"a[", "ab", false, ErrBadPattern, true},
 	{"*x", "xxx", true, nil, true},
 	{"[abc]", "b", true, nil, true},