Remove redundant Auspice build

[victorlin]

Description of proposed changes

Auspice has a prepare script that runs the build script automatically after npm install. This means the explicit call to run the build script is redundant and can be removed to improve build times.

Related issue(s)

Testing

• Checks pass
• nextstrain view --docker --image nextstrain/base:branch-victorlin-remove-redundant-auspice-build works

[victorlin]

CI passes, but nextstrain view is unable to find '/nextstrain/auspice/dist' and fails.

I think this has to do with the upgrade to Node.js 16. Compare 1afd07d (which introduces the Node.js 16 upgrade) and the previous commit f8ea4da. Node.js 14 logs only show one occurrence of node auspice.js build --verbose while Node.js 16 logs show two (one being redundant).

Both NPM v7 (packaged with Node.js 14) and NPM v8 (packaged with Node.js 16) docs say that the prepare script should run on local npm install (and this is what I've observed on my local machine), so I'm not sure why there is a difference in behavior here. But given what's observed, this change should be bundled with the upgrade to Node.js 16.