Remove return types

Since we don't add return types like this right now, it's best to keep things consistent.

Author: driesvints

src/Illuminate/Filesystem/FilesystemAdapter.php

@@ -562,7 +562,7 @@ public function size($path)
      *
      * @throws UnableToProvideChecksum
      */
-    public function checksum(string $path, array $options = []): string|false
+    public function checksum(string $path, array $options = [])
     {
         try {
             return $this->driver->checksum($path, $options);