Fix erb installation failure

[soutaro]

Bundler cannot reinstall erb-6.0.1 because there's a previous installation of it
at /opt/hostedtoolcache/Ruby/4.0.1/x64/lib/ruby/gems/4.0.0/gems/erb-6.0.1 that
is unsafe to remove.
The parent of
/opt/hostedtoolcache/Ruby/4.0.1/x64/lib/ruby/gems/4.0.0/gems/erb-6.0.1 is
world-writable and does not have the sticky bit set, making it insecure to
remove due to potential vulnerabilities.
Please change the permissions of
/opt/hostedtoolcache/Ruby/4.0.1/x64/lib/ruby/gems/4.0.0/gems or choose a
different install path.

Installing erb explicitly solves the issue.