Fix for engine requires

MSP-11412

## Verification steps

- [ ] `rake spec`


## Post-merge steps

- [x] Remove the `PRERELEASE` line from `version.rb`
- [x] Remove the line for `metasploit-concern` in the `Gemfile`
- [x] Remove the line for `metasploit-model` in the `Gemfile`
- [x] Remove the comment from following line in the `gemspec`:

```ruby
s.add_runtime_dependency 'metasploit-concern'#, '~> 0.3.0'
```

- [x] Remove the comment from following line in the `gemspec`:

```ruby
s.add_runtime_dependency 'metasploit-model'#,'~> 0.28.0'
```
        
- [x] `bundle`
- [ ] Commit and push to master
- [ ] Make a new RubyGems release