C#: Update test expected output.

Author: michaelnebel

csharp/ql/test/query-tests/Language Abuse/MissedReadonlyOpportunity/MissedReadonlyOpportunity.expected

@@ -1,7 +1,3 @@
-#select
 | MissedReadonlyOpportunity.cs:3:16:3:19 | Bad1 | Field 'Bad1' can be 'readonly'. |
 | MissedReadonlyOpportunity.cs:4:14:4:17 | Bad2 | Field 'Bad2' can be 'readonly'. |
-| MissedReadonlyOpportunity.cs:11:20:11:24 | Good7 | Field 'Good7' can be 'readonly'. |
 | MissedReadonlyOpportunityBad.cs:3:9:3:13 | Field | Field 'Field' can be 'readonly'. |
-testFailures
-| MissedReadonlyOpportunity.cs:11:20:11:24 | Field 'Good7' can be 'readonly'. | Unexpected result: Alert |