Part 3: Mark accountManager as 'lazy' in Mode.kt

This is enough to cause it to be initialized only if we're going through onboarding.

app/src/main/java/org/mozilla/fenix/home/Mode.kt

@@ -50,7 +50,7 @@ class CurrentMode(
     private val dispatchModeChanges: (mode: Mode) -> Unit
 ) : AccountObserver {
 
-    private val accountManager = context.components.backgroundServices.accountManager
+    private val accountManager by lazy { context.components.backgroundServices.accountManager }
 
     fun getCurrentMode() = if (onboarding.userHasBeenOnboarded()) {
         Mode.fromBrowsingMode(browsingModeManager.mode)