Remove axios dependency

[domharrington]

Just use fetch()?

[cvan]

• for any GitHub API requests, octokit can be called from the already installed @actions/github package.
• for the existing Bitbucket API, there's this npm package bitbucket, which is a pretty nice octokit-esque Node client.

tl;dr: it's probably safe to just use plain old fetch. or, if folks are stuck running versions of node earlier than v18 (~v17.5 added fetch), GitHub recommends using @actions/http-client.

paranoid: if build sizes & times become an issue, using Node's builtin https module to make HTTP requests would work just fine (there are quite a few examples in the @vercel, @actions, @netlify, … orgs).