Remove native return type from __toString() test to avoid lint failure

The native `never` return type on `__toString()` causes a lint error
since PHP requires `__toString()` to declare `string` as its return type.
Use a `@return never` PHPDoc instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Rules/Exceptions/CatchWithUnthrownExceptionRuleTest.php

@@ -739,7 +739,7 @@ public function testBug13806(): void
 		$this->analyse([__DIR__ . '/data/bug-13806.php'], [
 			[
 				'Dead catch - Throwable is never thrown in the try block.',
-				27,
+				28,
 			],
 		]);
 	}

tests/PHPStan/Rules/Exceptions/data/bug-13806.php

@@ -14,7 +14,8 @@ function castToString(\Stringable|string $variable): string {
 }
 
 class MyString {
-	public function __toString(): never {
+	/** @return never */
+	public function __toString() {
 		throw new \Exception();
 	}
 }