build: remove outdated travisci config

.travis.yml

@@ -1,21 +0,0 @@
-os:
-  - linux
-  - osx
-language: node_js
-node_js:
-  - '12'
-  - '10'
-dist: xenial
-sudo: required
-services:
-  - xvfb
-before_script:
-  - export DISPLAY=:99.0
-install:
-  - npm set progress=false
-  - npm install
-script:
-  - ng lint
-  - npm run test
-  - npm run e2e
-  - npm run build