[backport][v6] fix: GKE cluster update behavior

[matttrach]

Tracking:
Main issue: #1499
Master PR: #1518
Backport PR: #1525

[rishabhmsra]

Tested the bug fix on rancher v2.10-head with rancher2 provider v6.7.0-rc1, updating the node count doesn't require recreation of cluster, new nodes gets added successfully, hence this can be closed.