fix incorrect insertion order of stylesheets (facebook#28108)

## Summary

In the precendences Map every key is prefixed with `p`. This fixes one
case where this is missing.

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Author: sokra

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -3559,7 +3559,7 @@ function insertStylesheetIntoRoot(
   if (prior === last) {
     precedences.set('last', instance);
   }
-  precedences.set(precedence, instance);
+  precedences.set('p' + precedence, instance);
 
   this.count++;
   const onComplete = onUnsuspend.bind(this);