Fixed error shown in console when importing GKE

[eva-vashkevich]

Summary

Fixes #13562

Moved nodePools configuration to non-imported block, since cluster import doesn't need it and doesn't have them defined

Occurred changes and/or fixed issues

Technical notes summary

Areas or cases that should be tested

• Import GKE -> select credential -> no error should be shown in the console
• Edit imported GKE -> no error should be shown in the console
• Create GKE -> no error should be shown in the console
• Edit existing GKE -> no error should be shown in the console

Areas which could experience regressions

GKE provisioning and import (both create and edit)

Screenshot/Video

Checklist

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[momesgin]

tested and lgtm