scripts/update-gh-pages: fix release version parsing

[marquiz]

When determining the release branch only consider "main" release tags, refusing to pick api/nfd/v* tags.

[k8s-ci-robot]

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[marquiz]

Needs to be backported to release-0.16 branch to fix #1971
/cherry-pick release-0.16
/assign @TessaIO

[k8s-infra-cherrypick-robot]

@marquiz: once the present PR merges, I will cherry-pick it on top of release-0.16 in a new PR and assign it to you.

In response to this:

Needs to be backported to release-0.16 branch to fix #1971
/cherry-pick release-0.16
/assign @TessaIO

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[marquiz]

/retest

[marquiz]

/assign @ArangoGutierrez

[TessaIO]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: e8d145d5eea4633134e5dfe07250ddc56d42564f

[k8s-infra-cherrypick-robot]

@marquiz: new pull request created: #1975

In response to this:

Needs to be backported to release-0.16 branch to fix #1971
/cherry-pick release-0.16
/assign @TessaIO

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.