MFH: r493213 r493610 r495827

Remove outdated comment

The corresponding patches of the 2 ports which contain rubygems version have
been replaced by REINPLACE_CMD command in r486416 and r486417.

Update devel/ruby-gems to 3.0.2

• Update Mk/Uses/gem.mk

Changes: https://github.com/rubygems/rubygems/blob/master/History.txt
PR: 235795
Submitted by: Yasuhiro KIMURA <yasu@utahime.org>, sunpoet (myself)
Exp-run by: antoine

Update to 3.0.3

Changes: https://github.com/rubygems/rubygems/blob/master/History.txt
Security: 27b12d04-4722-11e9-8b7c-b5e01141761f

Approved by: ports-secteam (joneum)