fix(phpstan): remove redundant is_string check

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Naoray

src/Tracing/InertiaDataCollector.php

@@ -107,7 +107,7 @@ protected function extractComponentFromResponse($response): ?string
 
         // Try to parse component from JSON response
         $content = $response->getContent();
-        if (! $content || ! is_string($content)) {
+        if ($content === false || $content === '') {
             return null;
         }