README polaris overview link is broken

[YuweiXiao]

Describe the bug

https://polaris.apache.org/in-dev/unreleased/overview/

To Reproduce

No response

Actual Behavior

No response

Expected Behavior

No response

Additional context

No response

System information

No response

[adnanhemani]

I believe the new link is https://polaris.apache.org/in-dev/unreleased/ as per #1605. You can always also access by going to polaris.apache.org and then clicking the "Get Started" button :)

[flyrain]

@adnanhemani is right. We moved the Overview page to the index page.