Reflect Discourse default of HTTPS (#482)

Reflect Discourse default of HTTPS (#482)

Discourse installs HTTPS as standard, so mail-receiver should probably reflect this too.

diff --git a/samples/mail-receiver.yml b/samples/mail-receiver.yml
index 9035b4b..bd7859e 100644
--- a/samples/mail-receiver.yml
+++ b/samples/mail-receiver.yml
@@ -29,7 +29,7 @@ env:
   ## This is simply your forum's base URL, with `/admin/email/handle_mail`
   ## appended.  Be careful if you're running a subfolder setup -- in that case,
   ## the URL needs to have the subfolder included!
-  DISCOURSE_MAIL_ENDPOINT: 'http://discourse.example.com/admin/email/handle_mail'
+  DISCOURSE_MAIL_ENDPOINT: 'https://discourse.example.com/admin/email/handle_mail'
 
   ## The master API key of your Discourse forum.  You can get this from
   ## the "API" tab of your admin panel.

GitHub sha: 468f1f9c

This commit appears in #482 which was approved by riking. It was merged by riking.