💅 Normalize security doc title capitalization

Author: webknjaz

SECURITY.md

@@ -18,7 +18,7 @@ vulnerability report via GitHub directly. To do so, follow these instructions:
 4. Click the green `Submit report` button at the bottom.
 
 
-## Don't have a GitHub account?
+## Don't Have a GitHub Account?
 
 Alternatively, drop an email to our [aio-libs security] mailbox instead of
 filing a ticket or posting to _any_ public groups. It is currently set up to