[Predictive Back] Fix custom predictive back implementations and update androidx.activity dependency to 1.8.0-alpha06.

PiperOrigin-RevId: 544098906

Author: afohrman

build.gradle

@@ -22,7 +22,7 @@ ext {
   targetSdkVersion = 33
 
   androidXVersions = [
-    activity                     : '1.8.0-alpha05',
+    activity                     : '1.8.0-alpha06',
     annotation                   : '1.2.0',
     appCompat                    : '1.6.1',
     cardView                     : '1.0.0',

catalog/build.gradle

@@ -16,7 +16,7 @@ dependencies {
   api 'androidx.constraintlayout:constraintlayout:2.1.0'
   api 'androidx.gridlayout:gridlayout:1.0.0'
   api "androidx.multidex:multidex:2.0.1"
-  api "androidx.activity:activity:1.8.0-alpha05"
+  api "androidx.activity:activity:1.8.0-alpha06"
   api "androidx.recyclerview:recyclerview:1.2.1"
   api 'androidx.window:window:1.0.0-beta04'
   api "androidx.window:window-java:1.0.0-beta04"