Liquid: mark getSmallestFlowDecay() as impure

this fixes two bogus PHPStan warnings.

src/pocketmine/block/Liquid.php

@@ -418,6 +418,9 @@ abstract class Liquid extends Transparent{
 		return $isOptimalFlowDirection;
 	}
 
+	/**
+	 * @phpstan-impure This function modifies the adjacent sources count (premature optimisation)
+	 */
 	private function getSmallestFlowDecay(Block $block, int $decay) : int{
 		$blockDecay = $this->getFlowDecay($block);
 

tests/phpstan/configs/phpstan-bugs.neon

@@ -1,15 +1,5 @@
 parameters:
 	ignoreErrors:
-		-
-			message: "#^Comparison operation \"\\>\\=\" between 0 and 2 is always false\\.$#"
-			count: 1
-			path: ../../../src/pocketmine/block/Liquid.php
-
-		-
-			message: "#^If condition is always false\\.$#"
-			count: 1
-			path: ../../../src/pocketmine/block/Liquid.php
-
 		-
 			message: "#^Call to function is_resource\\(\\) with resource will always evaluate to true\\.$#"
 			count: 3