Remove unnecessary #[RequiresPhp] from testBug6934

RuleTestCase uses php-parser which can parse nullsafe syntax on any
PHP version, so #[RequiresPhp('>= 8.0')] is not needed. Other nullsafe
tests in this file (e.g. testNullSafe) run without this attribute.

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

Author: 2 people

tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php

@@ -3945,7 +3945,6 @@ public function testBug7369(): void
 		]);
 	}
 
-	#[RequiresPhp('>= 8.0')]
 	public function testBug6934(): void
 	{
 		$this->checkThisOnly = false;