Increase the default number of rpc serving threads

This may be responsible for the timeouts on Windows CI, maybe clients
aren't closing their connections in the same way?

Anyway, it's a small enough change that it shouldn't wreck performance,
and it's worth it to check if this fixes this pain in the butt CI issue.

Author: carver

trin-core/src/cli.rs

@@ -44,7 +44,7 @@ pub struct TrinConfig {
     pub web3_ipc_path: String, // TODO: Change to PathBuf
 
     #[structopt(
-        default_value = "2",
+        default_value = "5",
         long = "pool-size",
         help = "max size of threadpool"
     )]