Update runtime-control.md

[RMDavidson]

Removed gerund from line 22 - controlling vs control

Proposed changes

Write a clear and concise description that helps reviewers understand the purpose and impact of your changes. Use the
following format:

Problem: Removing gerunds from headers in this topic.

Solution: Removed gerund from Controlling NGINX so it reads Control NGINX. This topic only had one header that needed to be changed.

Testing: N/A

Please focus on (optional): If you any specific areas where you would like reviewers to focus their attention or provide
specific feedback, add them here.

If this PR addresses an issue on GitHub, ensure that you link to it here:

Closes #ISSUE

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[mjang]

Thanks!