.travis.yml: Remove notification config

This is enabled by default actually.

.travis.yml

@@ -6,9 +6,5 @@ before_script: git clone https://github.com/alanorth/hugo-theme-bootstrap4-blog.
 script: hugo
 sudo: false
 dist: trusty
-notifications:
-  email:
-    on_success: never
-    on_failure: always
 
 # vim: ts=2 sw=2 et