Migrate from AndroidManifest to build.gradle for namespace

AGP has deprecated use of packageName in AndroidManifest and
instead wants everyone to use `android { namespace = "foo" }`
in build.gradle files.

Test: ./gradlew tasks -> still passes
Change-Id: I4fa03cacc7214011f3797c36dcb76c2984c7bf52
diff --git a/navigation/navigation-dynamic-features-runtime/build.gradle b/navigation/navigation-dynamic-features-runtime/build.gradle
index 347d0cf..8365a88 100644
--- a/navigation/navigation-dynamic-features-runtime/build.gradle
+++ b/navigation/navigation-dynamic-features-runtime/build.gradle
@@ -27,6 +27,7 @@
     defaultConfig {
         multiDexEnabled true
     }
+    namespace "androidx.navigation.dynamicfeatures"
 }
 
 dependencies {