[test] Add failing test for mutating global

compiler/forget/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/mutate-global-increment-op-invalid-react.expect.md

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+
+## Input
+
+```javascript
+let renderCount = 0;
+
+function NoHooks() {
+  renderCount++;
+  return <div />;
+}
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+let renderCount = 0;
+
+function NoHooks() {
+  const $ = useMemoCache(1);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = <div />;
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+```
+      

compiler/forget/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/mutate-global-increment-op-invalid-react.js

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+let renderCount = 0;
+
+function NoHooks() {
+  renderCount++;
+  return <div />;
+}