chore(client): minor internal fixes

Author: stainless-app[bot]

src/client.ts

@@ -579,17 +579,17 @@ export class Stainless {
   }
 
   buildRequest(
-    options: FinalRequestOptions,
+    inputOptions: FinalRequestOptions,
     { retryCount = 0 }: { retryCount?: number } = {},
   ): { req: FinalizedRequestInit; url: string; timeout: number } {
-    options = { ...options };
+    const options = { ...inputOptions };
     const { method, path, query } = options;
 
     const url = this.buildURL(path!, query as Record<string, unknown>);
     if ('timeout' in options) validatePositiveInteger('timeout', options.timeout);
     options.timeout = options.timeout ?? this.timeout;
     const { bodyHeaders, body } = this.buildBody({ options });
-    const reqHeaders = this.buildHeaders({ options, method, bodyHeaders, retryCount });
+    const reqHeaders = this.buildHeaders({ options: inputOptions, method, bodyHeaders, retryCount });
 
     const req: FinalizedRequestInit = {
       method,