Remove `expect` call from `gateway-cli`

[justinmoon]

Lots of expect call here. If the command failed, print message to STDERR. But don't panic.

[elsirion]

main already returns a Result:

https://github.com/fedimint/fedimint/blob/e5178267b58f184797c0fea2b004b83b8a12adbb/gateway/cli/src/main.rs#L66-L67

What happens if it's Err? If it does the right thin, we can just replace expect with ? everywhere. If not we might want a main_inner function and then do the logging in case of errors in main.

[okjodom]

Good first issue claimed offline by @nassersaazi . Please post any questions or progress updates in this thread

[justinmoon]

Closed by #1993