chore: remove install.sh script and documentation references (#8643)

* chore: remove install.sh script and documentation references

- Delete docs/static/install.sh (broken installer causing issues)
- Remove One-Line Installer section from linux.md documentation
- Remove install.sh references from installation/_index.en.md
- Remove install.sh warning and commands from README.md

Closes #8032

* fix: add missing closing braces to notice shortcode