fix(audience-sdk): use namespace-URI-aware lookup in AndroidManifestPostProcessor

Replace prefix-dependent `Attributes["android:name"]` with
`Attributes.GetNamedItem("name", AndroidNs)` so the duplicate-permission
check uses the same namespace-URI lookup as the SetAttribute insertion,
making both sides of the guard consistent.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nattb8

src/Packages/Audience/Editor/AndroidManifestPostProcessor.cs

@@ -35,7 +35,7 @@ public void OnPostGenerateGradleAndroidProject(string path)
             foreach (XmlNode node in root.ChildNodes)
             {
                 if (node.Name == "uses-permission" &&
-                    node.Attributes?["android:name"]?.Value == InternetPermission)
+                    node.Attributes?.GetNamedItem("name", AndroidNs)?.Value == InternetPermission)
                     return;
             }