Make BuildsQueries::tap consistent with other versions of tap (#38359)

Author: axlon

src/Illuminate/Database/Concerns/BuildsQueries.php

@@ -422,10 +422,12 @@ protected function cursorPaginator($items, $perPage, $cursor, $options)
      * Pass the query to a given callback.
      *
      * @param  callable  $callback
-     * @return $this|mixed
+     * @return $this
      */
     public function tap($callback)
     {
-        return $this->when(true, $callback);
+        $callback($this);
+
+        return $this;
     }
 }