Fill in release date for 5.2.6

CHANGELOG.txt

@@ -1,7 +1,7 @@
 Changelog
 =========
 
-5.2.6 (xx.xx.xxxx) - IN DEVELOPMENT
+5.2.6 (11.07.2024)
 ~~~~~~~~~~~~~~~~~~
 
  * Fix: CVE-2024-39317: Regular expression denial-of-service via search query parsing (Jake Howard)

docs/releases/5.2.6.md

@@ -1,6 +1,6 @@
-# Wagtail 5.2.6 release notes - IN DEVELOPMENT
+# Wagtail 5.2.6 release notes
 
-_Unreleased_
+_July 11, 2024_
 
 ```{contents}
 ---