Update colors on create button in private story creation flow.

app/src/main/res/layout/stories_create_with_recipients_fragment.xml

@@ -68,7 +68,8 @@
             android:layout_marginEnd="16dp"
             android:layout_marginBottom="16dp"
             android:text="@string/CreateStoryWithViewersFragment__create"
-            android:textColor="@color/white"
+            android:textColor="@color/signal_colorOnPrimaryContainer"
+            app:backgroundTint="@color/signal_colorPrimaryContainer"
             app:cornerRadius="80dp"
             app:elevation="4dp"
             app:layout_constraintBottom_toBottomOf="parent"