Upgrade to play-services-basement:18.1.0

Upgraded firebase-messaging from 23.0.0 -> 23.0.8, which upgrades to
play-services-basement:18.1.0.

Removed direct dependency reference to
com.google.android.gms:play-services-base. Version locking isn't
recommened for this specific dependency, since other things depend
on it like com.google.firebase:firebase-messaging.

Author: jkasten2

OneSignalSDK/onesignal/notifications/build.gradle

@@ -69,23 +69,13 @@ dependencies {
 
     compileOnly('com.amazon.device:amazon-appstore-sdk:[3.0.1, 3.0.99]')
 
-    // play-services-base:16.1.0 is the last version before going to AndroidX
-    // play-services-base:17.0.0 is the first version using AndroidX
-    // Required for GoogleApiAvailability
-    implementation('com.google.android.gms:play-services-base') {
-        version {
-            require '[17.0.0, 17.6.99]'
-            prefer '17.6.0'
-        }
-    }
-
     // firebase-messaging:18.0.0 is the last version before going to AndroidX
     // firebase-messaging:19.0.0 is the first version using AndroidX
     // firebase-messaging:23.0.0 incoporates fix for SecurityException: Not allowed to bind to service
     api('com.google.firebase:firebase-messaging') {
         version {
             require '[19.0.0, 23.0.99]'
-            prefer '23.0.0'
+            prefer '23.0.8'
         }
     }