fix: don't override user-agent

I've been having problems with websites treating my user-agent as Android, which makes sense because Firefox is literally reporting itself as Android. Sometimes websites that have mobile apps stop the user from using the web app in favor of the Android app, which isn't ideal because this isn't an Android device.

Slack is the primary example for this. I've been able to work around it by using the Header Editor browser extension to modify my user-agent.

Reference: #39 (comment 1463350879)

This adheres to a comment made by @ollieparanoid (#39 (comment 1463350879)) proposing that we drop Android from the user-agent, and stop overriding it entirely. This is a Linux device after all, and we expect websites to follow best practices, including responsive design that doesn't depend on the user-agent.

Related

• Alternative to and closes !33 (closed)
• Closes #43 (closed)
• Closes #39 (closed)