[5.0.x] Fixed typo in docs/howto/custom-file-storage.txt.

Signed-off-by: cuinix <915115094@qq.com>

Backport of 20848bcf39de891bcf865b47f6f5f550e3f21958 from main

docs/howto/custom-file-storage.txt

@@ -133,7 +133,7 @@ to refer to a specific storage throughout Django, to a dictionary of settings
 for that specific storage backend. The settings in the inner dictionaries are
 described fully in the :setting:`STORAGES` documentation.
 
-Storages are then accessed by alias from from the
+Storages are then accessed by alias from the
 :data:`django.core.files.storage.storages` dictionary::
 
     from django.core.files.storage import storages