[Common] Remove outdated check (#7396)

The check still verified if the app was running in ICS, deprecated long
ago.

Internal b/446049497

Author: rlazo

agents.md

@@ -194,4 +194,4 @@ After you make a change, here's the flow you should follow:
 ## Updating this Guide
 
 If new patterns or conventions are discovered, update this guide to ensure it remains a useful
-resource.
+resource.

firebase-common/src/main/java/com/google/firebase/FirebaseApp.java

@@ -37,7 +37,6 @@
 import com.google.android.gms.common.api.internal.BackgroundDetector;
 import com.google.android.gms.common.internal.Objects;
 import com.google.android.gms.common.internal.Preconditions;
-import com.google.android.gms.common.util.PlatformVersion;
 import com.google.android.gms.common.util.ProcessUtils;
 import com.google.firebase.components.Component;
 import com.google.firebase.components.ComponentDiscovery;
@@ -689,8 +688,7 @@ private static class GlobalBackgroundStateListener
         new AtomicReference<>();
 
     private static void ensureBackgroundStateListenerRegistered(Context context) {
-      if (!(PlatformVersion.isAtLeastIceCreamSandwich()
-          && context.getApplicationContext() instanceof Application)) {
+      if (!(context.getApplicationContext() instanceof Application)) {
         return;
       }
       Application application = (Application) context.getApplicationContext();