Display real fedimint block finality delay

[tvolk131]

The fedimint on-chain receive description is hard-coded to say "10 block confirmations":

harbor/harbor-ui/src/routes/receive.rs

Line 153 in 1191c03

"Good for large amounts. Requires on-chain fees and 10 block confirmations.",

While 10 blocks is the default, this block finality delay is configurable by the federation guardians. I added support for fetching the actual finality delay to the fedimint-wallet-client crate in this PR: fedimint/fedimint#7657

Once this change lands in fedimint v0.9, let's use the new function to display the actual finality delay for a given federation.

[tvolk131]

Update: Fedimint v0.9 is out, and this functionality is now exposed in fedimint (see here)