Update go version to 1.21

[Amulyam24]

What this PR does / why we need it:
Updates go version to 1.21

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:

/area provider/ibmcloud

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

Update go version to 1.21

[netlify]

✅ Deploy Preview for kubernetes-sigs-cluster-api-ibmcloud ready!

Name	Link
🔨 Latest commit	5a9b489
🔍 Latest deploy log	https://app.netlify.com/sites/kubernetes-sigs-cluster-api-ibmcloud/deploys/65cf4b5ff8aaa90008cf0f0a
😎 Deploy Preview	https://deploy-preview-1621--kubernetes-sigs-cluster-api-ibmcloud.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[Amulyam24]

/cc @Prajyot-Parab @mkumatag

[Amulyam24]

Will be creating a PR for updating the kubekins image to 1.28 in test-infra

[mkumatag]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Amulyam24, mkumatag

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [mkumatag]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[Prajyot-Parab]

@Amulyam24 @mkumatag we should be cherry picking this one right.

[mkumatag]

@Prajyot-Parab I see go.* files changes as well, not sure if cherrypick really works.. please create a separate PR to update the version

[Prajyot-Parab]

@Prajyot-Parab I see go.* files changes as well, not sure if cherrypick really works.. please create a separate PR to update the version

will do.