package/putty: drop optional dependency on libgtk2

As we're about to remove libgtk2, we need to drop the optional
dependency of putty on libgtk2.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>

package/putty/putty.mk

@@ -14,8 +14,6 @@ PUTTY_CONF_OPTS = -DPUTTY_GSSAPI=OFF
 
 ifeq ($(BR2_PACKAGE_LIBGTK3),y)
 PUTTY_DEPENDENCIES += libgtk3
-else ifeq ($(BR2_PACKAGE_LIBGTK2),y)
-PUTTY_DEPENDENCIES += libgtk2
 endif
 
 ifeq ($(BR2_STATIC_LIBS),y)