Added release date for 2.2.15 and 3.0.9.

docs/releases/2.2.15.txt

@@ -2,7 +2,7 @@
 Django 2.2.15 release notes
 ===========================
 
-*Expected August 3, 2020*
+*August 3, 2020*
 
 Django 2.2.15 fixes two bugs in 2.2.14.
 

docs/releases/3.0.9.txt

@@ -2,7 +2,7 @@
 Django 3.0.9 release notes
 ==========================
 
-*Expected August 3, 2020*
+*August 3, 2020*
 
 Django 3.0.9 fixes several bugs in 3.0.8.