Use relative installation root instead of absolute to avoid embedding absolute paths in pods project (#33187)

Summary:
Use relative installation root instead of absolute to avoid embedding absolute paths in pods project
Also removes a leading space from each path.

Before:

<img width="799" alt="155846827-94c474b7-8a79-45fc-a900-8860a94fb318" src="https://user-images.githubusercontent.com/996231/155847731-de128759-bff5-4d1f-a59a-377298055d85.png">

After:

<img width="745" alt="Screenshot 2022-02-26 at 15 58 32" src="https://user-images.githubusercontent.com/996231/155847739-b783debc-a805-4ce7-a88a-33f764dc5985.png">

## Changelog

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[iOS] [Fixed] - Remove absolute paths from pods project

Pull Request resolved: https://github.com/facebook/react-native/pull/33187

Test Plan: Pod install and view in Xcode FBReactNativeSpec -> Build Phases -> [CP-User] Generate Specs

Reviewed By: ShikaSD

Differential Revision: D34549541

Pulled By: dmitryrykun

fbshipit-source-id: 2926b093fb87f50ef9988e23fce593348f00077d

packages/rn-tester/NativeModuleExample/ScreenshotManager.podspec

@@ -25,7 +25,7 @@ Pod::Spec.new do |s|
   s.source_files    = "**/*.{h,m,mm,swift}"
   s.requires_arc    = true
 
-  s.dependency "React"
+  s.dependency "React-Core"
   s.dependency "RCT-Folly", folly_version
 
   # s.dependency "..."