Switches settings to use the light holo theme

PreferenceCategory titles don't inherit the theme correctly, but
this seems to be a frameworks issue. See b/2569810 and b/2308250
for related bugs.

Change-Id: I6890e273740071fbd6603c292276bccee1f81270
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 75208ec..e8f97e4 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -97,7 +97,8 @@
         </activity>
 
         <activity android:name="SelectCalendarsActivity" android:label="@string/calendars_title" />
-        <activity android:name="CalendarSettingsActivity" android:label="@string/preferences_title" />
+        <activity android:name="CalendarSettingsActivity" android:label="@string/preferences_title"
+            android:theme="@android:style/Theme.Light.Holo"/>
 
         <!-- Declarations for search -->
         <!-- Make all activities a searchable context -->