test: remove support for EOL versions of Node.js

Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Christian Clauss <cclauss@me.com>
Reviewed-By: Rod Vagg <rod@vagg.org>

.travis.yml

@@ -13,14 +13,6 @@ jobs:
       env: NODE_GYP_FORCE_PYTHON=python2
       python: 2.7
 
-    - name: "Node.js 6 & Python 3.8 on Linux"
-      python: 3.8
-      env: NODE_GYP_FORCE_PYTHON=python3
-      before_install: nvm install 6
-    - name: "Node.js 8 & Python 3.8 on Linux"
-      python: 3.8
-      env: NODE_GYP_FORCE_PYTHON=python3
-      before_install: nvm install 8
     - name: "Node.js 10 & Python 3.8 on Linux"
       python: 3.8
       env: NODE_GYP_FORCE_PYTHON=python3
@@ -56,14 +48,6 @@ jobs:
       env: NODE_GYP_FORCE_PYTHON=python3 PATH=$HOME/.pyenv/shims:$PATH PYENV_VERSION=3.8.0
       before_install: pyenv install $PYENV_VERSION
 
-    - name: "Node.js 6 & Python 2.7 on Windows"
-      os: windows
-      language: node_js
-      node_js: 6  # node
-      env: >-
-        PATH=/c/Python27:/c/Python27/Scripts:$PATH
-        NODE_GYP_FORCE_PYTHON=/c/Python27/python.exe
-      before_install: choco install python2
     - name: "Node.js 12 & Python 2.7 on Windows"
       os: windows
       language: node_js