Documentation: fix typos in name of application folder

The name is "application/", not "applications/".

(This commit does not change managing_apps.rst,
 where "applications/" is used intentionally).
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 9ca01d8..55927f2 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -2399,7 +2399,7 @@
 -  Moved the list of "allowed URI characters" out of the Router class
    and into the config file.
 -  Moved the MIME type array out of the Upload class and into its own
-   file in the applications/config/ folder.
+   file in the application/config/ folder.
 -  Updated the Upload class to allow the upload field name to be set
    when calling :doc:`do_upload() <./libraries/file_uploading>`.
 -  Updated the :doc:`Config Library <./libraries/config>` to be able to