fix: issue when using let with http protocol

- the type of the second argument was changed from `string` to `mixed`

src/Core/Traits/SurrealTrait.php

@@ -94,7 +94,7 @@ public function getScope(): ?string
      * @param string $value
      * @return null
      */
-    public function let(string $param, string $value): null
+    public function let(string $param, mixed $value): null
     {
         $this->params[$param] = $value;
         return null;