docs: Add :no-index: to module directives to fix duplicate warnings

why: Sphinx warns about duplicate object descriptions when the same module
is referenced in multiple documentation files.
what:
- Add :no-index: directive to module blocks in windows.md, pytest-plugin/index.md,
  and quickstart.md to prevent duplicate indexing

Author: tony

docs/api/windows.md

@@ -7,7 +7,7 @@
 - Identified by `@`, e.g. `@313`
 
 ```{module} libtmux
-
+:no-index:
 ```
 
 ```{eval-rst}

docs/pytest-plugin/index.md

@@ -13,7 +13,7 @@ your case, we won't stabilize APIs until we're sure everything is by the book.
 [connect with us]: https://github.com/tmux-python/libtmux/discussions
 
 ```{module} libtmux.pytest_plugin
-
+:no-index:
 ```
 
 ## Usage

docs/quickstart.md

@@ -129,7 +129,7 @@ $ ptpython
 ```
 
 ```{module} libtmux
-
+:no-index:
 ```
 
 First, we can grab a {class}`Server`.