don't depend on phpstan 0.12.4 phpdoc inheriting

this causes build failure because the parameter names are different to
the base class.

src/pocketmine/level/generator/noise/Perlin.php

@@ -151,6 +151,12 @@ class Perlin extends Noise{
 		*/
 	}
 
+	/**
+	 * @param float $x
+	 * @param float $y
+	 *
+	 * @return float
+	 */
 	public function getNoise2D($x, $y){
 		return $this->getNoise3D($x, $y, 0);
 	}

src/pocketmine/level/generator/noise/Simplex.php

@@ -266,6 +266,12 @@ class Simplex extends Perlin{
 		return 32.0 * $n;
 	}
 
+	/**
+	 * @param float $x
+	 * @param float $y
+	 *
+	 * @return float
+	 */
 	public function getNoise2D($x, $y){
 		$x += $this->offsetX;
 		$y += $this->offsetY;