Enable Web3Modal on Polygon Checkout

[nfrgosselin]

User Story:
As a grant donor
I want to checkout on Polygon with wallets other than Metamask
So that I am not tied to using one wallet

Acceptance Criteria
GIVEN that I am on /grants/cart AND have Polygon-eligible grants in my cart AND do not have a wallet connected
WHEN I click "Polygon checkout"
THEN I see the Web3Modal to select a wallet

GIVEN that I am on /grants/cart AND have Polygon-eligible grants in my cart AND have a Web3Modal-eligible wallet connected
WHEN I click "Polygon checkout"
THEN I am able to checkout

Product & Design Links:

Tech Details:
@chibie has documented the required steps for this here

Open Questions:

Notes/Assumptions:
Follow-on story from #10482

[nfrgosselin]

@chibie I was able to test Coinbase end-to-end and the integration worked successfully.

However, when I tried to use Portis,Fortmatic, and Wallet connect I could go through the login flow fine, then I would get this error:

Any ideas?

[chibie]

@nfrgosselin Coinbase changes aren't in this PR but WIP here -> #10410. did you mean MetaMask?

for the other wallet types, were you on mainnet/rinkeby?

[chibie]

this pr fixes the bug -> #10606