Rename GKE as Kubernetes Engine

What does this MR do?

Rename Google Container Engine as Kubernetes Engine.

Are there points in the code the reviewer needs to double check?

There are two occurrences to leave as they should remain.

doc/articles/index.md

| Video Tutorial: Idea to Production on Google Container Engine (GKE) | Tutorial | 2017-01-23 |

The original title remains unchanged.

doc/integration/google.md

1. From the Dashboard select ENABLE APIS AND SERVICES > Google Cloud APIs > Container Engine API > Enable

Google has not changed the API name on their API dashboard.

Why was this MR needed?

To avoid notation divergence from Google's.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• [n/a] API support added
• [n/a] Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • [n/a] Has been reviewed by Backend
  • [n/a] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #40537 (closed)