Simplify isContextSensitive (microsoft#17722)

Author: Andy

src/compiler/checker.ts

@@ -8367,7 +8367,8 @@ namespace ts {
             switch (node.kind) {
                 case SyntaxKind.FunctionExpression:
                 case SyntaxKind.ArrowFunction:
-                    return isContextSensitiveFunctionLikeDeclaration(<FunctionExpression>node);
+                case SyntaxKind.MethodDeclaration:
+                    return isContextSensitiveFunctionLikeDeclaration(<FunctionExpression | ArrowFunction | MethodDeclaration>node);
                 case SyntaxKind.ObjectLiteralExpression:
                     return forEach((<ObjectLiteralExpression>node).properties, isContextSensitive);
                 case SyntaxKind.ArrayLiteralExpression:
@@ -8380,9 +8381,6 @@ namespace ts {
                         (isContextSensitive((<BinaryExpression>node).left) || isContextSensitive((<BinaryExpression>node).right));
                 case SyntaxKind.PropertyAssignment:
                     return isContextSensitive((<PropertyAssignment>node).initializer);
-                case SyntaxKind.MethodDeclaration:
-                case SyntaxKind.MethodSignature:
-                    return isContextSensitiveFunctionLikeDeclaration(<MethodDeclaration>node);
                 case SyntaxKind.ParenthesizedExpression:
                     return isContextSensitive((<ParenthesizedExpression>node).expression);
                 case SyntaxKind.JsxAttributes: