Do not generate ReactCodegen.podspec for libraries (#50645)

Summary:
Pull Request resolved: #50645

While we were refactoring the generation of the podspec, we made a mistake and we started generating the ReactCodegen.podspec for both libraries and apps.

This must be generated only for apps.

## Changelog:
[iOS][Fixed] - Generate `ReactCodegen.podspec` only for apps.

Reviewed By: fabriziocucci

Differential Revision: D72854074

fbshipit-source-id: 5a1d1120e576d4fe4cf8f733793f5a2619278c2b

Author: cipolleschi

packages/react-native/scripts/codegen/generate-artifacts-executor/index.js

@@ -123,13 +123,13 @@ function execute(
           outputPath,
         );
         generateAppDependencyProvider(outputPath);
+        generateReactCodegenPodspec(
+          projectRoot,
+          pkgJson,
+          outputPath,
+          baseOutputPath,
+        );
       }
-      generateReactCodegenPodspec(
-        projectRoot,
-        pkgJson,
-        outputPath,
-        baseOutputPath,
-      );
 
       cleanupEmptyFilesAndFolders(outputPath);
     }