For tests, always allow parse option changes

src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs

@@ -680,5 +680,8 @@ public void ChangeSolution(Solution solution)
 
             this.RaiseWorkspaceChangedEventAsync(WorkspaceChangeKind.SolutionChanged, oldSolution, newSolution);
         }
+
+        public override bool CanApplyParseOptionChange(ParseOptions oldOptions, ParseOptions newOptions, Project project)
+        => true;
     }
 }