Fixes #2644: Update release docs to use pnpm

[menghif]

Issue This PR Addresses

Fixes #2644

Type of Change

• Bugfix: Change which fixes an issue
• New Feature: Change which adds functionality
• Documentation Update: Change which improves documentation
• UI: Change which improves UI

Description

This PR updates the release docs to use pnpm instead of npm. It also removes the section about running npm outdated before each release.
I haven't found any issues when using pnpm version so this should be the correct way of creating a new release.

Checklist

• Quality: This PR builds and passes our npm test and works locally
• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not (if applicable)
• Documentation: This PR includes updated/added documentation to user exposed functionality or configuration variables are added/changed or an explanation of why it does not(if applicable)

[gitpod-io]

[humphd]

At least we know this works!

[HyperTHD]

LGTM!