Pylance not installed - Revert to Jedi requires reload

[hediet]

Testing #18964

• In a single root-workspace

• In user settings, "python.languageServer": "Pylance", is configured

• No other settings

• Notification gets shown -> Click on "Revert to Jedi"

• Observe that intellisense still does not work

• Reload window

• Observe that intellisense does work now