Make getUnderlineColor public.

Bug: 117521361
Test: atest CtsTextTestCases:android.text.style.cts.SuggestionSpanTest
Change-Id: Iafc7fa65b495e5cc5e69809c94c15c947ceab9ca

api/current.txt

@@ -45847,6 +45847,7 @@ package android.text.style {
     method public deprecated java.lang.String getLocale();
     method public java.util.Locale getLocaleObject();
     method public int getSpanTypeId();
+    method public int getUnderlineColor();
     method public java.lang.String[] getSuggestions();
     method public void setFlags(int);
     method public void updateDrawState(android.text.TextPaint);

core/java/android/text/style/SuggestionSpan.java

@@ -369,10 +369,7 @@ public class SuggestionSpan extends CharacterStyle implements ParcelableSpan {
 
     /**
      * @return The color of the underline for that span, or 0 if there is no underline
-     *
-     * @hide
      */
-    @UnsupportedAppUsage
     public int getUnderlineColor() {
         // The order here should match what is used in updateDrawState
         final boolean misspelled = (mFlags & FLAG_MISSPELLED) != 0;