ci: switch region from eastus to westus2

[binbin-li]

Description

What this PR does / why we need it:

Currently the aks test is failing due to unavailable SKU in eastus region. The exact error:

ERROR: (SkuNotAvailable) Preflight validation check for resource(s) for container service ratify-aks-cb3d in resource group MC_ratify-e2e-cb3d_ratify-aks-cb3d_eastus failed. Message: The requested VM size for resource 'Following SKUs have failed for Capacity Restrictions: Standard_DS3_v2' is currently not available in location 'eastus'. Please try another size or deploy to a different location or different zone. See https://aka.ms/azureskunotavailable for details.. Details: 

The required SKU is supported in westus2. Tested in my forked repo:

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

Fixes #

Type of change

Please delete options that are not relevant.

• 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 not work as expected)
• Helm Chart Change (any edit/addition/update that is necessary for changes merged to the main branch)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• Test A
• Test B

Checklist:

• Does the affected code have corresponding tests?
• Are the changes documented, not just with inline documentation, but also with conceptual documentation such as an overview of a new feature, or task-based documentation like a tutorial? Consider if this change should be announced on your project blog.
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have appropriate license header?

Post Merge Requirements

• MAINTAINERS: manually trigger the "Publish Package" workflow after merging any PR that indicates Helm Chart Change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅