doc: add powershell uninstall instructions (command)

Author: Kartones

docs/_index.md

@@ -189,6 +189,16 @@ curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poet
 ```
 {{% /warning %}}
 
+If you installed Poetry via Powershell:
+```powershell
+(Invoke-WebRequest -Uri https://install.python-poetry.org -UseBasicParsing).Content | py - --uninstall
+```
+
+{{% note %}}
+If you have installed Python through the Microsoft Store, replace `py` with `python` in the command
+above.
+{{% /note %}}
+
 {{< /step >}}
 {{< /steps >}}