chore: clearer error message when function signature does not contain parentheses

[yipu3]

Component

Cast

Describe the feature you would like

When I wrongly input a function signature without parentheses:

./target/debug/cast call 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D 'deposit'

The error message is a bit of confusing:

Error: If you wish to fetch function data from EtherScan, please provide an API key.

And cost me some time the figure out what's the point.

A clearer error message is needed.

Additional context

No response

[yipu3]

Have created a pr to fix.
#9478