Fix typo

Co-authored-by: Hans Glimmerfors <hans_glimmerfors@hotmail.com>

Author: SergioInToronto

lib/cachex.ex

@@ -573,7 +573,7 @@ defmodule Cachex do
   You may provide a third element in a `:commit` Tuple, to specify options the
   same as you would in `put/4`.
 
-  Multilpe calls to `fetch/4` with the same key while the `fallback` is running
+  Multiple calls to `fetch/4` with the same key while the `fallback` is running
   will wait on the lazy evaluation to complete. Multiple instances of
   `fallback` will never run concurrently for a given key.