CAPI: Update milestone applier config for v1.7

[furkatgofurov7]

Part of: kubernetes-sigs/cluster-api#9094 and addresses: https://github.com/kubernetes-sigs/cluster-api/blob/main/docs/release/release-tasks.md#create-a-release-branch:

Update the [milestone applier config](https://github.com/kubernetes/test-infra/blob/0b17ef5ffd6c7aa7d8ca1372d837acfb85f7bec6/config/prow/plugins.yaml#L371) accordingly (e.g. release-1.4: v1.4 and main: v1.5)
Prior art: https://github.com/kubernetes/test-infra/pull/266315

/hold until release-1.6 branch is created

[furkatgofurov7]

This can be already reviewed, it is just we should keep the hold label until the release-1.6 branch is created (November 14th).

cc @killianmuldoon @sbueringer
/assign @dims

for approval when you have time, thanks

[killianmuldoon]

/lgtm

[sbueringer]

/approve

[cblecker]

/approve

[dims]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cblecker, dims, furkatgofurov7, sbueringer

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[sbueringer]

/hold cancel

[k8s-ci-robot]

@furkatgofurov7: Updated the plugins configmap in namespace default at cluster test-infra-trusted using the following files:

• key plugins.yaml using file config/prow/plugins.yaml

In response to this:

Part of: kubernetes-sigs/cluster-api#9094 and addresses: https://github.com/kubernetes-sigs/cluster-api/blob/main/docs/release/release-tasks.md#create-a-release-branch:

Update the [milestone applier config](https://github.com/kubernetes/test-infra/blob/0b17ef5ffd6c7aa7d8ca1372d837acfb85f7bec6/config/prow/plugins.yaml#L371) accordingly (e.g. release-1.4: v1.4 and main: v1.5)
Prior art: https://github.com/kubernetes/test-infra/pull/266315

/hold until release-1.6 branch is created

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