Revert "pkg: hint at PHP version, pkg is too conservative here"

This reverts commit c4628a0b.
It looks like pkg can't handle php70 to php71 at all.

Makefile

@@ -98,7 +98,6 @@ CORE_DEPENDS?=		apinger \
 			pecl-radius${CORE_PHP} \
 			pftop \
 			phalcon${CORE_PHP} \
-			php${CORE_PHP} \
 			php${CORE_PHP}-ctype \
 			php${CORE_PHP}-curl \
 			php${CORE_PHP}-dom \