[cfe] Remove NnbdModeMismatch

Change-Id: I27d1f63050f1e4ab4b7f57e25e6287ab27f49f09
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416480
Reviewed-by: Jens Johansen <[email protected]>
Commit-Queue: Jens Johansen <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>
Auto-Submit: Johnni Winther <[email protected]>

Author: johnniwinther

pkg/front_end/test/incremental_suite.dart

@@ -425,10 +425,6 @@ const String EXPECTATIONS = '''
     "name": "InitializedFromDillMismatch",
     "group": "Fail"
   },
-  {
-    "name": "NNBDModeMismatch",
-    "group": "Fail"
-  },
   {
     "name": "ConstantCoverageReferenceWithoutNode",
     "group": "Fail"
@@ -473,7 +469,6 @@ final Expectation LibraryCountMismatch =
     staticExpectationSet["LibraryCountMismatch"];
 final Expectation InitializedFromDillMismatch =
     staticExpectationSet["InitializedFromDillMismatch"];
-final Expectation NNBDModeMismatch = staticExpectationSet["NNBDModeMismatch"];
 final Expectation ConstantCoverageReferenceWithoutNode =
     staticExpectationSet["ConstantCoverageReferenceWithoutNode"];