Update graphics language to comply with Android’s inclusive language guidance

Bug: 161896447
Test: make

See https://source.android.com/setup/contribute/respectful-code for reference

Change-Id: I57b81fb5fd2177fbf96f9cc900097f7da1955fca

graphics/java/android/graphics/Region.java

@@ -409,10 +409,10 @@ public class Region implements Parcelable {
         mNativeRegion = ni;
     }
 
-    /* add dummy parameter so constructor can be called from jni without
+    /* Add an unused parameter so constructor can be called from jni without
        triggering 'not cloneable' exception */
     @UnsupportedAppUsage
-    private Region(long ni, int dummy) {
+    private Region(long ni, int unused) {
         this(ni);
     }