Fix: update outdated git repository URL in documentation

The documentation still referenced the old Git URL. Updated it to the correct repository: [email protected]:EOS-Contrib/eos_plugin_for_unity_upm.git.

Author: JessTello

com.playeveryware.eos/Documentation~/add_plugin.md

@@ -16,7 +16,7 @@ The following document outlines the two methods with which you can add the plugi
     ![Unity Add Git Package](/com.playeveryware.eos/Documentation~/images/unity_package_git.gif)
 
 4. Select `Add Package from Git URL`.
-6. Paste in `[email protected]:PlayEveryWare/eos_plugin_for_unity_upm.git`.
+6. Paste in `[email protected]:EOS-Contrib/eos_plugin_for_unity_upm.git`.
 7. After the package has finished installing, [import the samples](/com.playeveryware.eos/Documentation~/samples.md).
 8. Finally, [Configure the Plugin](/com.playeveryware.eos/Documentation~/configure_plugin.md).