Downgrade k8s version for clusterctl upgrade spec

[pydctw]

What type of PR is this?
/kind failing-test

What this PR does / why we need it:
clusterctl v1alpha3 upgrade spec on main is failing with the following message. See failing test

[6] • Failure [847.960 seconds]
[6] [unmanaged] [Cluster API Framework]
[6] /home/prow/go/src/sigs.k8s.io/cluster-api-provider-aws/test/e2e/suites/unmanaged/unmanaged_CAPI_test.go:34
[6]   Clusterctl Upgrade Spec [from v1alpha3]
[6]   /home/prow/go/src/sigs.k8s.io/cluster-api-provider-aws/test/e2e/suites/unmanaged/unmanaged_CAPI_test.go:155
[6]     Should create a management cluster and then upgrade all the providers [It]
[6]     /home/prow/go/pkg/mod/sigs.k8s.io/cluster-api/test@v1.0.1-0.20211111175208-4cc2fce2111a/e2e/clusterctl_upgrade.go:145
[6] 
[6]     failed to run clusterctl init:
      
[6]     Error: unsupported management cluster server version: v1.22.2 - versions greater or equal than v1.22.0 are not supported

Downgrading k8s version to 1.21.6 to fix the failing test and unblock main.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:
An issue is raised in CAPI for a long term solution by @sedefsavas - kubernetes-sigs/cluster-api#5704

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

None

[k8s-ci-robot]

@pydctw: This issue is currently awaiting triage.

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[pydctw]

/test pull-cluster-api-provider-aws-e2e

[Ankitasw]

/lgtm

[Ankitasw]

/priority critical-urgent

[sedefsavas]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sedefsavas

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