Add RequiresPhp >= 8.0.0 to testBug14542 and regenerate baseline

The test uses `mixed` type which requires PHP 8.0+. Baseline
regenerated with `make phpstan-generate-baseline` to fix entry ordering.

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

Author: phpstan-bot

phpstan-baseline.neon

@@ -18,6 +18,12 @@ parameters:
 			count: 1
 			path: src/Analyser/ArgumentsNormalizer.php
 
+		-
+			rawMessage: Casting to string something that's already string.
+			identifier: cast.useless
+			count: 3
+			path: src/Analyser/ExprHandler/AssignHandler.php
+
 		-
 			rawMessage: 'Doing instanceof PHPStan\Type\Constant\ConstantStringType is error-prone and deprecated. Use Type::getConstantStrings() instead.'
 			identifier: phpstanApi.instanceofType
@@ -48,12 +54,6 @@ parameters:
 			count: 1
 			path: src/Analyser/Ignore/IgnoredErrorHelperResult.php
 
-		-
-			rawMessage: Casting to string something that's already string.
-			identifier: cast.useless
-			count: 3
-			path: src/Analyser/ExprHandler/AssignHandler.php
-
 		-
 			rawMessage: Casting to string something that's already string.
 			identifier: cast.useless

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -1543,6 +1543,7 @@ public function testBug14501(): void
 		$this->assertNoErrors($errors);
 	}
 
+	#[RequiresPhp('>= 8.0.0')]
 	public function testBug14542(): void
 	{
 		$errors = $this->runAnalyse(__DIR__ . '/data/bug-14542.php');