Fork the postfix cookbook to work around a bug

I ran into the issue described in
https://github.com/sous-chefs/postfix/issues/148
and couldn't figure out a way to work around it without forking it.

Berksfile.lock

@@ -28,7 +28,10 @@ DEPENDENCIES
   ohai (~> 5.2.5)
   openssl (~> 8.5.5)
   php (~> 8.0.0)
-  postfix (~> 6.0.26)
+  postfix
+    git: https://gitea.kosmos.org/kosmos/postfix-cookbook.git
+    revision: dd6598572a775ae73f17527260ec8097b52d385b
+    ref: bugfix/
   redisio (~> 6.4.1)
   ruby_build (~> 2.5.0)
   timezone_iii (= 1.0.4)
@@ -90,7 +93,7 @@ GRAPH
   openssl (8.5.5)
   php (8.0.1)
     yum-epel (>= 0.0.0)
-  postfix (6.0.26)
+  postfix (6.4.1)
   redisio (6.4.1)
     selinux (>= 0.0.0)
   ruby_build (2.5.0)