[TOOL-3606] playground: Remove Ethereum as default selected chain in insight playground (#6413)

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## PR-Codex overview
This PR refines the logic for setting default values in the `values` object within the `blueprint-playground.client.tsx` file. It consolidates the conditions for assigning a default value to parameters.

### Detailed summary
- Removed the specific check for `param.name === "chain"` that assigned a hardcoded value of `"1"`.
- Simplified the condition to check if `param.schema` has a `type` and a `default` property.
- Updated the assignment of `values[param.name]` to use `param.schema.default` when applicable, otherwise setting it to an empty string.

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Author: MananTank

apps/playground-web/src/app/insight/[blueprint_slug]/blueprint-playground.client.tsx

@@ -157,13 +157,7 @@ export function BlueprintPlaygroundUI(props: {
   const defaultValues = useMemo(() => {
     const values: Record<string, string | number> = {};
     for (const param of parameters) {
-      if (param.name === "chain") {
-        values.chain = "1";
-      } else if (
-        param.schema &&
-        "type" in param.schema &&
-        param.schema.default
-      ) {
+      if (param.schema && "type" in param.schema && param.schema.default) {
         values[param.name] = param.schema.default;
       } else {
         values[param.name] = "";