Change PreferenceController#getSummary return type.

Return CharSequence instead of String.

All user visible string should be modeled as CharSequence.

Bug: 73950519
Test: robotest in settings CL
Change-Id: Ied2384fa520e5e4665f79dae9df66dbcf2f106b6

packages/SettingsLib/src/com/android/settingslib/core/AbstractPreferenceController.java

@@ -72,9 +72,9 @@ public abstract class AbstractPreferenceController {
 
 
     /**
-     * @return a String for the summary of the preference.
+     * @return a {@link CharSequence} for the summary of the preference.
      */
-    public String getSummary() {
+    public CharSequence getSummary() {
         return null;
     }
 }