Revert "Set NPM_CONFIG_STRICT_SSL=false for Node.js 0.8"

This reverts commit cb25482a49.

.travis.yml

@@ -1,8 +1,6 @@
 language: node_js
 before_install:
-  # Old npm certs are untrusted https://github.com/npm/npm/issues/20191
-  - 'if [ "${TRAVIS_NODE_VERSION}" = "0.8" ]; then export NPM_CONFIG_STRICT_SSL=false; fi'
-  - 'nvm install-latest-npm'
+  - nvm install-latest-npm
 matrix:
   include:
   - node_js: '0.8'