chore: Update CircleCI config (#661)

Removing a couple extraneous CircleCI commands to see if they're still needed. I think one of the removed lines is causing #654 to fail, but let's see.

.circleci/config.yml

@@ -10,8 +10,6 @@ jobs:
     <<: *defaults
     steps:
       - checkout
-      # For some reason phantomjs-prebuild is failing w/yarn, but npm installing works
-      - run: 'npm install --no-save phantomjs-prebuilt'
       - run: 'yarn install'
       - run: 'yarn lint:ci'
       - run: 'yarn build:ci'
@@ -34,7 +32,6 @@ jobs:
           at: ~/project
       - checkout
       - run: 'yarn install'
-      - run: 'yarn add karma-cli --dev'
       - run: 'yarn test:web --maxWorkers=4'
       - run: 'yarn build:web:ci --maxWorkers=4'