Use rntester-legacy URL scheme for legacy arch app (#50670)

Summary:
Pull Request resolved: #50670

Changelog: [internal]

Reviewed By: shwanton

Differential Revision: D72840476

fbshipit-source-id: 8fca3241c54b70fc3267cfcf30211035eb595a25

Author: NickGerleman

packages/rn-tester/js/RNTesterAppShared.js

@@ -153,7 +153,7 @@ const RNTesterApp = ({
       // *  rntester://example/<moduleKey>
       // *  rntester://example/<moduleKey>/<exampleKey>
       const match =
-        /^rntester:\/\/example\/([a-zA-Z0-9_-]+)(?:\/([a-zA-Z0-9_-]+))?$/.exec(
+        /^rntester(-legacy)?:\/\/example\/([a-zA-Z0-9_-]+)(?:\/([a-zA-Z0-9_-]+))?$/.exec(
           url,
         );
       if (!match) {
@@ -163,8 +163,8 @@ const RNTesterApp = ({
         return;
       }
 
-      const rawModuleKey = match[1];
-      const exampleKey = match[2];
+      const rawModuleKey = match[2];
+      const exampleKey = match[3];
 
       // For tooling compatibility, allow all these variants for each module key:
       const validModuleKeys = [