x11-toolkits/itk: drop major version from LIB_DEPENDS for itcl

lang/itcl installs both libitcl.so and libitcl.so.3. Major version
for the itcl hadn'b been changed for years, so no breakage should be
seen: looks like this change can be made at the time of commit
ddb5a7b884735b58415ebdc7736d2bbbb70aa0c7.

Signed-off-by: Eygene Ryabinkin <rea@FreeBSD.org>
Approved by: yuri (mentor)