Do not set the release date until it has been really released.

hippo91 · hippo91 · commit 9270a2105fa7 · 2020-12-29T14:19:10.000+01:00
diff --git a/ChangeLog b/ChangeLog
@@ -5,7 +5,8 @@ astroid's ChangeLog
 
 What's New in astroid 2.5.0?
 ============================
-Release Date: 2020-12-27
+Release Date: TBA
+
 
 * Add `python 3.9` support.
 
