Renamed "Font Back Color" to "Highlight Color" on Android Viewer

Change-Id: Ia87a8091cf7ca7f15b9be7d5368f314d20421258
Signed-off-by: Mert Tumer <merttumer@outlook.com>
Reviewed-on: https://gerrit.libreoffice.org/58283
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

android/source/res/layout/toolbar_bottom.xml

@@ -384,7 +384,7 @@
                                     <TextView
                                         android:layout_width="wrap_content"
                                         android:layout_height="wrap_content"
-                                        android:text="Font Back Color"
+                                        android:text="Highlight Color"
                                         android:paddingBottom="12dp"
                                         android:paddingTop="12dp"
                                         android:textSize="14sp"