upgrade rollup in both unlock-app and paywall

[cellog]

Description

This PR upgrades rollup, and its plugins. It also swaps out rollup-plugin-uglify for rollup-plugin-terser because of webpack-contrib/terser-webpack-plugin#15 (and similar discussions in many other projects, and lots of buzz on twitter discussing similar improvements with terser vs. uglify.

Issues

Fixes #1675

Checklist:

• 1 PR, 1 purpose: my Pull Request applies to a single purpose
  • This PR only contains configuration changes (package.json, etc.)
  • This PR only contains code changes (if configuration changes are required, do a separate PR first, then re-base)
• My code follows the style guidelines of this project, including naming conventions
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• If my code adds or changes components, I have written corresponding stories with Storybook
• I have performed a self-review of my own code
• If my code involves visual changes, I am adding applicable screenshots to this thread

[nfurfaro]

Looks good Greg!