Remove send calls in PagesWorker and GitlabShellWorker

We should remove the #send calls in

• PagesWorker
• GitlabShellWorker.

These are already flagged by the GitlabSecurity/PublicSend cop.

While Sidekiq arguments in these cases are expected to not come from user input, it can be abused in situations where Redis is compromised.

/cc @gitlab-com/gl-security/appsec