Fix node pool update when MachinePool version is set

[kahun]

What type of PR is this?
/kind bug

What this PR does / why we need it:
When the version is defined in the MachinePool object, the following error occurs in the reconciliation process:

E1211 13:28:24.009959 1 gcpmanagedmachinepool_controller.go:342] "msg"="Reconcile error" "error"="node pool config update (either version/labels/taints/locations/image type/network tag or all) failed: rpc error: code = InvalidArgument desc = Version "v1.27.3-gke.100" is invalid. It should have the form 1.X, 1.X.Y, 1.X.Y-.*, 'latest'

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Fix GKE reconciliation process when MachinePool version is set.

[k8s-ci-robot]

Hi @kahun. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[cpanato]

/ok-to-test

[richardcase]

This looks ok to me.

@kahun could you update the release note please?

[richardcase]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kahun, richardcase

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