Remove extra space under "Wi-Fi hotspot" option

Due to the attribute "settings:summaryLineCount" cause the extra space,
use "android:maxLines" instead of the original attribute.

Bug: 186609481
Test: Manual test
Change-Id: Id0beeeddfab443a4434f53b7575af0966e3371d7
diff --git a/res/xml/tether_prefs.xml b/res/xml/tether_prefs.xml
index d86f420..97ad5fd 100644
--- a/res/xml/tether_prefs.xml
+++ b/res/xml/tether_prefs.xml
@@ -29,7 +29,7 @@
         android:summary="@string/summary_placeholder"
         android:fragment="com.android.settings.wifi.tether.WifiTetherSettings"
         settings:allowDividerAbove="true"
-        settings:summaryLineCount="2"/>
+        settings:maxLines="2"/>
 
     <com.android.settingslib.RestrictedSwitchPreference
         android:key="usb_tether_settings"