fix: neutron grpc url default; url parsing error message (#3466)

### Description

The default neturon grpc url is plaintext but it was using a `http`
prefix so all requests would fail

### Drive-by changes

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### Related issues

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- Fixes #[issue number here]
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### Backward compatibility

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implications, e.g. changes that would prohibit deploying older commits
using this infra tooling?

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### Testing

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rust/config/mainnet3_config.json

@@ -482,7 +482,7 @@
       ],
       "grpcUrls": [
         {
-          "http": "https://grpc-kralum.neutron-1.neutron.org:80"
+          "http": "http://grpc-kralum.neutron-1.neutron.org:80"
         }
       ],
       "canonicalAsset": "untrn",

rust/hyperlane-base/src/settings/parser/mod.rs

@@ -422,7 +422,7 @@ fn parse_custom_urls(
         .end()
         .map(|urls| {
             urls.split(',')
-                .filter_map(|url| url.parse().take_err(err, || &chain.cwp + "customGrpcUrls"))
+                .filter_map(|url| url.parse().take_err(err, || &chain.cwp + key))
                 .collect_vec()
         })
 }
@@ -440,12 +440,12 @@ fn parse_base_and_override_urls(
 
     if combined.is_empty() {
         err.push(
-            &chain.cwp + "rpc_urls",
-            eyre!("Missing base rpc definitions for chain"),
+            &chain.cwp + base_key,
+            eyre!("Missing base {} definitions for chain", base_key),
         );
         err.push(
             &chain.cwp + "custom_rpc_urls",
-            eyre!("Also missing rpc overrides for chain"),
+            eyre!("Also missing {} overrides for chain", base_key),
         );
     }
     combined