Fill in release date for 4.0.3

CHANGELOG.txt

@@ -87,7 +87,7 @@ Changelog
  * Fix: Update latest version message on Dashboard to accept dev build version format used on nlightly builds (Sam Moran)
 
 
-4.0.3 (xx.xx.xxxx) - IN DEVELOPMENT
+4.0.3 (18.10.2022)
 ~~~~~~~~~~~~~~~~~~
 
  * Render `help_text` when set on `FieldPanel`, `MultiFieldPanel`, `FieldRowPanel`, and other panel APIs where it previously worked without official support (Matt Westcott)

docs/releases/4.0.3.md

@@ -1,6 +1,6 @@
 # Wagtail 4.0.3 release notes
 
-_Unreleased_
+_October 18, 2022_
 
 ```{contents}
 ---