remove &$var reference notations in phpdoc

this isn't required by the spec and PHPStan chokes on it. I was previously having it ignore these errors, but it turns out that PHPStan is not making use of extended typeinfo provided if it can't parse the tag, which is problematic on level 6 and also a problem for array-of-type. Therefore, we are going to have to take the hit.

src/pocketmine/level/format/io/region/McRegion.php

@@ -331,8 +331,8 @@ class McRegion extends BaseLevelProvider{
 	/**
 	 * @param int $chunkX
 	 * @param int $chunkZ
-	 * @param int &$regionX
-	 * @param int &$regionZ
+	 * @param int $regionX reference parameter
+	 * @param int $regionZ reference parameter
 	 */
 	public static function getRegionIndex(int $chunkX, int $chunkZ, &$regionX, &$regionZ){
 		$regionX = $chunkX >> 5;

src/pocketmine/level/format/io/region/RegionLoader.php

@@ -244,8 +244,8 @@ class RegionLoader{
 
 	/**
 	 * @param int $offset
-	 * @param int &$x
-	 * @param int &$z
+	 * @param int $x reference parameter
+	 * @param int $z reference parameter
 	 */
 	protected static function getChunkCoords(int $offset, ?int &$x, ?int &$z) : void{
 		$x = $offset & 0x1f;