docs(contributing): remove npm dist tags requirement

The npm dist tags are not worth the hassle, and are arguably harmful to the Web. Developers should feel encouraged to always test the latest available Puppeteer & Chromium versions, as opposed to any specific version.

Issue: #6482

CONTRIBUTING.md

@@ -289,19 +289,3 @@ Releasing to npm consists of the following phases:
 1. Source Code: mark post-release.
     1. Bump `package.json` version to the `-post` version, run `npm run doc` to update the “released APIs” section at the top of `docs/api.md` accordingly, and send a PR titled `'chore: bump version to vXXX.YYY.ZZZ-post'` ([example](https://github.com/puppeteer/puppeteer/commit/d02440d1eac98028e29f4e1cf55413062a259156))
         - **NOTE**: no other commits should be landed in-between release commit and bump commit.
-
-## Updating npm dist tags
-
-For both `puppeteer` and `puppeteer-core` we maintain `chrome-*` npm dist tags, e.g. `chrome-75` and so on. These tags match the Puppeteer version that corresponds to the `chrome-*` release.
-
-These tags are updated on every Puppeteer release.
-
-Managing tags 101:
-
-```bash
-# List tags
-$ npm dist-tag ls puppeteer
-# Add tags
-$ npm dist-tag add puppeteer@3.0.0 chrome-81
-$ npm dist-tag add puppeteer-core@3.0.0 chrome-81
-```