Secure our notification email.

Forks will have to define their own
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1821)

.travis.yml

@@ -127,5 +127,4 @@ after_success:
 
 notifications:
     email:
-        - openssl-commits@openssl.org
-
+        secure: "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"