Switch Fragment and Navigation to use Activity prebuilts

There's no notable changes in Activity, so we
can temporarily switch to Activity 1.1.0-alpha03
prebuilts to avoid unnecessary releases.

Test: ./gradlew bOS
Change-Id: Ie6599337839c14b2e0c5c6adcf7b3d4bc6593a8d
diff --git a/navigation/navigation-runtime/build.gradle b/navigation/navigation-runtime/build.gradle
index 2624b7c..5b2ae45 100644
--- a/navigation/navigation-runtime/build.gradle
+++ b/navigation/navigation-runtime/build.gradle
@@ -28,7 +28,7 @@
 
 dependencies {
     api(project(":navigation:navigation-common"))
-    api(project(":activity:activity"))
+    api("androidx.activity:activity:1.1.0-alpha03")
     api(project(":lifecycle:lifecycle-viewmodel"))
     api("androidx.savedstate:savedstate:1.0.0-rc01")
     api(project(":lifecycle:lifecycle-viewmodel-savedstate"))