change tag to v120beta1

[longwuyuan]

What this PR does / why we need it:

• Change TAG to v1.2.0.beta-1

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

How Has This Been Tested?

Checked on close and test in CI + cloudbuild results

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

[k8s-ci-robot]

@longwuyuan: This issue is currently awaiting triage.

If Ingress contributors determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

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[rikatz]

/lgtm
/approve
Thanks

[tao12345666333]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: longwuyuan, rikatz, tao12345666333

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

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Needs approval from an approver in each of these files:

• OWNERS [rikatz]

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