Use pre-installed nodejs until we need multiple Node.js version.

Author: exoego

.travis.yml

@@ -7,9 +7,6 @@ jdk:
 scala:
   - 2.13.0
 
-install:
-  - rm -rf ~/.nvm && git clone https://github.com/creationix/nvm.git ~/.nvm && (cd ~/.nvm && git checkout `git describe --abbrev=0 --tags`) && source ~/.nvm/nvm.sh && nvm install $TRAVIS_NODE_VERSION
-
 script:
   - admin/build.sh
 
@@ -22,8 +19,7 @@ env:
     # SONA_PASS
     - secure: "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"
   matrix:
-    - TRAVIS_NODE_VERSION="10.16.0"
-      SCALAJS_VERSION="0.6.28"
+    - SCALAJS_VERSION="0.6.28"
 
 before_cache:
   - find $HOME/.sbt -name "*.lock" | xargs rm