docs(contributing): clarify list of Chromium versions (#5878)

CONTRIBUTING.md

@@ -233,7 +233,7 @@ Releasing to npm consists of the following phases:
 1. Source Code: mark a release.
     1. Bump `package.json` version following the SEMVER rules.
     2. Run `npm run doc` to update the docs accordingly.
-    3. Update the “Releases per Chromium Version” list in [`docs/api.md`](https://github.com/puppeteer/puppeteer/blob/master/docs/api.md) to include the new version.
+    3. Update the “Releases per Chromium Version” list in [`docs/api.md`](https://github.com/puppeteer/puppeteer/blob/master/docs/api.md) to include the new version. Note: only do this when the Chrome revision is different from the previous release.
     4. Send a PR titled `'chore: mark version vXXX.YYY.ZZZ'` ([example](https://github.com/puppeteer/puppeteer/pull/5078)).
     5. Make sure the PR passes **all checks**.
         - **WHY**: there are linters in place that help to avoid unnecessary errors, e.g. [like this](https://github.com/puppeteer/puppeteer/pull/2446)

docs/api.md

@@ -6,10 +6,6 @@
 - API Translations: [中文|Chinese](https://zhaoqize.github.io/puppeteer-api-zh_CN/#/)
 - Troubleshooting: [troubleshooting.md](https://github.com/puppeteer/puppeteer/blob/master/docs/troubleshooting.md)
 - Releases per Chromium Version:
-  * Chromium 81.0.4044.0 - [Puppeteer v3.0.4](https://github.com/puppeteer/puppeteer/blob/v3.0.4/docs/api.md)
-  * Chromium 81.0.4044.0 - [Puppeteer v3.0.3](https://github.com/puppeteer/puppeteer/blob/v3.0.3/docs/api.md)
-  * Chromium 81.0.4044.0 - [Puppeteer v3.0.2](https://github.com/puppeteer/puppeteer/blob/v3.0.2/docs/api.md)
-  * Chromium 81.0.4044.0 - [Puppeteer v3.0.1](https://github.com/puppeteer/puppeteer/blob/v3.0.1/docs/api.md)
   * Chromium 81.0.4044.0 - [Puppeteer v3.0.0](https://github.com/puppeteer/puppeteer/blob/v3.0.0/docs/api.md)
   * Chromium 80.0.3987.0 - [Puppeteer v2.1.0](https://github.com/puppeteer/puppeteer/blob/v2.1.0/docs/api.md)
   * Chromium 79.0.3942.0 - [Puppeteer v2.0.0](https://github.com/puppeteer/puppeteer/blob/v2.0.0/docs/api.md)