pkg/fileutils: TestMatches: remove cases no longer valid for go1.16

These tests were no longer valid on Go 1.16; related to https://tip.golang.org/doc/go1.16#path/filepath

> The Match and Glob functions now return an error if the unmatched part of
> the pattern has a syntax error. Previously, the functions returned early on
> a failed match, and thus did not report any later syntax error in the pattern.

Causing the test to fail:

    === RUN   TestMatches
        fileutils_test.go:388: assertion failed: error is not nil: syntax error in pattern: pattern="a\\" text="a"
    --- FAIL: TestMatches (0.00s)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 2842639e0e)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/fileutils/fileutils_test.go

@@ -377,8 +377,6 @@ func TestMatches(t *testing.T) {
 	if runtime.GOOS != "windows" {
 		tests = append(tests, []matchesTestCase{
 			{"a\\*b", "a*b", true},
-			{"a\\", "a", false},
-			{"a\\", "a\\", false},
 		}...)
 	}