Change the name of "Pull request open request" event in Audit log

Issue Summary

A typo in the Audit log event name for pull request creation.

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create a pull request
2. Open Audit log
3. Find the event 

Expected Results

Event name: Pull request open requested

Actual Results

Event name: Pull request open request

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available