www/grafana2: update 2.5.0 -> 2.6.0

• Update GH_ACCOUNT, GH_PROJECT, and GH_TAGNAME dependencies for 2.6.0
• Remove superfluous bsd.port.options.mk include
• Mute ${MKDIR} and ${MV} calls during post-extract

PR: 205450
Submitted by: Thomas Bartelmess <thomas@bartelmess.io> (maintainer)