Update image to rubygems-3.4
Related issue: #7 (closed)
Update RubyGems from 3.2 to 3.4.
Because prometheus-client-mmap >= 0.21.0 depends on RubyGems >= 3.3.22
and Gemfile depends on prometheus-client-mmap ~> 0.21,
RubyGems >= 3.3.22 is required.
So, because current RubyGems version is = 3.2.33,
version solving has failed.