Wiki Page Hook not supported?

## Issue

### Context
- **Gitlab plugin version**: 1.5.11
- **Gitlab version**: 11.8.2-ee
- **Jenkins version**: 2.165
- **Job type**: Matrix

### Logs & Traces

jenkins gitlab plugin log
```
WebHook called with url: /project/my_awesome_project
Nov 15, 2019 11:42:17 PM FINE com.dabsquared.gitlabjenkins.webhook.ActionResolver
Unsupported X-Gitlab-Event header: Wiki Page Hook
Nov 15, 2019 11:43:27 PM INFO com.dabsquared.gitlabjenkins.webhook.GitLabWebHook getDynamic
```

### Problem description

I have setup Gitlab webooks to notify jenkins in order to run builds for my project. **My webhook for "Push Events" operations work just fine**. However, "Wiki Page Events" do not work. If I perform the Hook operation "Test" it results in the following notification below:

`Hook executed successfully but returned HTTP 404 Error 404 Not Found

HTTP ERROR 404

Problem accessing /project/my_awesome_project. Reason:

 Not Found