Update the version support policy section in docs

[jbordonado]

Description

We caught up with the L-2 policy for WooCommerce a while ago, yet we are still mentioning a "loose policy" in our docs.

• https://github.com/Automattic/woocommerce-payments#version-support-policy
• https://github.com/Automattic/woocommerce-payments/blob/develop/docs/version-support-policy.md

[zmaglica]

Hi @jbordonado . Are you or team Harmony is planning to work on this issue? I have to prioritize it, and I am not sure will you (or team Harmony) will pick it up.

[jbordonado]

Hey, yes I guess Harmony will handle it