config-mail: Remove redundant colons from section titles

Change-Id: I7ce60624c694a97573166d8f78f89be6de77e55d
diff --git a/Documentation/config-mail.txt b/Documentation/config-mail.txt
index af2bd98..9eb31bf 100644
--- a/Documentation/config-mail.txt
+++ b/Documentation/config-mail.txt
@@ -10,7 +10,7 @@
 the template language for Gerrit emails. VTL has now been deprecated in favor of
 Soy, but Velocity templates that modify text emails remain supported for now.
 
-== Template Locations and Extensions:
+== Template Locations and Extensions
 
 The default example templates reside under:  `'$site_path'/etc/mail` and are
 terminated with the double extension `.soy.example`. Modifying these example
@@ -18,7 +18,7 @@
 example template to an equivalently named file without the `.example` extension
 and modifying it will allow an administrator to customize the template.
 
-== Supported Mail Templates:
+== Supported Mail Templates
 
 Each mail that Gerrit sends out is controlled by at least one template.  These
 are listed below.  Change emails are influenced by two additional templates,