TypeFamilies: should_compile/Simple20 fixed

testsuite/tests/ghc-regress/indexed-types/should_compile/all.T

@@ -20,7 +20,7 @@ test('Simple16', normal, compile, [''])
 test('Simple17', expect_fail, compile, [''])
 test('Simple18', normal, compile, [''])
 test('Simple19', normal, compile, [''])
-test('Simple20', expect_fail, compile, [''])
+test('Simple20', normal, compile, [''])
 
 test('ind1', normal, compile, [''])
 test('ind2', expect_fail_ways_if_compiler_lt('ghc','6.9',['profc','profasm']),