test: look for for "rc" instead of "beta" in react version

Author: lubieowoce

test/e2e/app-dir/rsc-basic/rsc-basic.test.ts

@@ -470,7 +470,7 @@ describe('app dir - rsc basics', () => {
 
   // TODO: (PPR) remove once PPR is stable
   const bundledReactVersionPattern =
-    process.env.__NEXT_EXPERIMENTAL_PPR === 'true' ? '-experimental-' : '-beta-'
+    process.env.__NEXT_EXPERIMENTAL_PPR === 'true' ? '-experimental-' : '-rc-'
 
   // TODO: (React 19) During Beta, bundled and installed version match.
   it.skip('should not use bundled react for pages with app', async () => {