Add 'Available on Ethereum mainnet' label for Governance and Staking

[iamanastasia]

Problem New members of the community are sometimes confused about using their l2 AAVE (e.g., Polygon network) to vote in Governance, or when staking. Current message (in the description) is hard to notice or find.

Possible solution If we put a more obvious label (NOT WARNING) it becomes more noticeable and will help users to avoid mistakes.

Alternative solutions —