Update ReleaseChecklist.md with new docs process

Author: zoobestik

docs/ReleaseChecklist.md

@@ -22,8 +22,6 @@ The following steps are usually performed:
 - Add a note describing what will be released to the [CHANGELOG](../CHANGELOG.md);
 - Bump up the current version in [gradle.properties](../gradle.properties);
 - Commit changes in `README`, `CHANGELOG` and `gradle.properties` into the `develop` branch;
-- Checkout `gh-pages` branch, generate documentation using Dokka (`./gradlew dokkaHtmlMultiModule`), move it to `docs` directory, and commit it all;
-  - that generated docs use correct `kotlinx-io` version;
 - [Deploy](https://teamcity.jetbrains.com/buildConfiguration/KotlinTools_KotlinxIo_DeployRunThisOne)
 a pre-release version of the library into [Sonatype](http://oss.sonatype.org) staging repository,
 close it and [run smoke tests](https://teamcity.jetbrains.com/buildConfiguration/KotlinTools_KotlinxIo_DeploymentSmokeTest) 
@@ -35,7 +33,7 @@ with this pre-release version;
   necessary;
   - release names are usually starts with `v`, like `v0.9.10`, but there's no `v` in a git tag, like `0.9.10`.
 - Deploy the release version, close the repo, run smoke tests with it and if tests passed, release the repository.
-- Push `gh-pages` branch;
+- Update version in `KOTLINX_IO_RELEASE_TAG` for [JetBrains/kotlin-web-site](https://github.com/JetBrains/kotlin-web-site/blob/master/.teamcity/BuildParams.kt#L7]
 - Set previously created draft in [kotlinx-io/releases](https://github.com/Kotlin/kotlinx-io/releases)
 as the latest version;
 - That's all, folks!