docs/quickstart.md(refactor): Update tmux requirements

why: Drop support for tmux versions older than 3.2
what:
- Remove "(recommended)" qualifier since 3.2a is now required
- Remove deprecation notice for tmux 1.8-3.1

Author: tony

docs/quickstart.md

@@ -12,8 +12,7 @@ from inside a live tmux session.
 
 ## Requirements
 
-- [tmux] 3.2a or newer (recommended)
-  - tmux 1.8 - 3.1 are deprecated and will be unsupported in a future release
+- [tmux] 3.2a or newer
 - [pip] - for this handbook's examples
 
 [tmux]: https://tmux.github.io/