docs: migrate peace.md out of docs (gnolang#1358)

## Description

This PR migrates `peace.md` out of the docs directory to the official
Gno blog, in [this](gnolang/blog#49) PR.

EDIT: Peace has been migrated to the blog, awaiting deployment. 

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

misc/docusaurus/sidebars.js

@@ -4,7 +4,6 @@
 const sidebars = {
  tutorialSidebar: [
  'overview',
- 'peace',
  {
  type: 'category',
  label: 'Getting Started',