refactor: Remove need for legacy code tests

Author: brettz9

test-d/index.test-d.ts

@@ -2,8 +2,6 @@ import { expectType, expectAssignable, expectError } from 'tsd';
 
 import { KEYS, getKeys, unionWith, VisitorKeys } from "../";
 
-type VisitorKeysWritable = { [type: string]: ReadonlyArray<string> };
-
 const assignmentExpression = {
     type: "AssignmentExpression",
     operator: "=",
@@ -39,29 +37,14 @@ expectType<{readonly [type: string]: readonly string[]}>(unionWith({
     TestInterface2: ["expression"]
 }));
 
-const keys: {
-    [type: string]: readonly string[]
-} = {
-    TestInterface1: ["left", "right"]
-};
-
 const readonlyKeys: {
     readonly [type: string]: readonly string[]
 } = {
     TestInterface1: ["left", "right"]
 };
 
-expectAssignable<VisitorKeysWritable>(keys);
-
 expectAssignable<VisitorKeys>(readonlyKeys);
 
-expectError(() => {
-    const erring: VisitorKeysWritable = {
-        TestInterface1: ["left", "right"]
-    };
-    erring.TestInterface1 = "badType";
-});
-
 // https://github.com/SamVerschueren/tsd/issues/143
 // expectError(() => {
 //     const erring: VisitorKeys = {