package/webkitgtk: drop unused flag

Upstream dropped in:
https://github.com/WebKit/WebKit/commit/aa6631a6189aaa4541a2d2e89993a4989103d161,
which is present since webkitgtk 2.36.4.

Signed-off-by: Thomas Devoogdt <thomas.devoogdt@barco.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/webkitgtk/webkitgtk.mk

@@ -78,7 +78,6 @@ endif
 # 2D CANVAS acceleration requires OpenGL proper with cairo-gl
 ifeq ($(BR2_PACKAGE_LIBGTK3_X11),y)
 WEBKITGTK_CONF_OPTS += \
-	-DENABLE_ACCELERATED_2D_CANVAS=ON \
 	-DENABLE_GLES2=OFF \
 	-DENABLE_X11_TARGET=ON
 WEBKITGTK_DEPENDENCIES += libgl \