fix(GdImage): imagedestroy is noop since PHP 8.0

Signed-off-by: Joas Schilling <coding@schilljs.com>

Author: nickvergessen

lib/private/Image.php

@@ -839,7 +839,6 @@ public function resize(int $maxSize): bool {
 			return false;
 		}
 		$result = $this->resizeNew($maxSize);
-		imagedestroy($this->resource);
 		$this->resource = $result;
 		return $this->valid();
 	}
@@ -875,7 +874,6 @@ public function preciseResize(int $width, int $height): bool {
 			return false;
 		}
 		$result = $this->preciseResizeNew($width, $height);
-		imagedestroy($this->resource);
 		$this->resource = $result;
 		return $this->valid();
 	}