Hide outlook threading hint

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

@@ -596,6 +596,7 @@
                     android:text="@string/title_advanced_gmail_thread_hint"
                     android:textAppearance="@style/TextAppearance.AppCompat.Small"
                     android:textStyle="italic"
+                    android:visibility="gone"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
                     app:layout_constraintTop_toBottomOf="@id/swOutlookThread" />