time.c: do not set utc_offset in vtm_add_offset
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66803 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
time.c: do not set utc_offset in vtm_add_offset
only. removed subtraction of utc_offset as it is overwritten
always immediately in callers.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66803 b2dd03c8-39d4-4d8f-98ff-823fe69b080e