LibDraw: Make [gs]et_pixel arguments used

Author: https://github.com/jcs
Commit: https://github.com/SerenityOS/serenity/commit/f5ecb31fc81
Pull-request: https://github.com/SerenityOS/serenity/pull/1177

Libraries/LibDraw/GraphicsBitmap.h

@@ -102,6 +102,8 @@ public:
     template<Format>
     Color get_pixel(int x, int y) const
     {
+        (void)x;
+        (void)y;
         ASSERT_NOT_REACHED();
     }
 
@@ -115,6 +117,8 @@ public:
     template<Format>
     void set_pixel(int x, int y, Color)
     {
+        (void)x;
+        (void)y;
         ASSERT_NOT_REACHED();
     }