Fix the Create new cluster feature

What does this MR do?

Fixes a ~bug on the Create new cluster feature for the GCP provider.

The feature broke suddenly because:

• We didn't pin a specific version of GKE
• The google API changed the default version to 1.19
• Google does not allow Basic Auth for 1.19 versions

This MR fixes by pinning the GKE version back at 1.18.

Still will need a better solution before 1.18 is completely removed from availability. &6049 (closed) seems the best candidate.

Relates to: #331582 (closed)

Conformity

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