remove suggestions to use Jupyter Lab workspace

as well as all mentions of how to open
a command line window or Python prompt in it,
as (for this tutorial) there's probably no advantage
to use Jupyter Lab in RunCode
over using RunCode's default VSCode based workspaces,
but indeed some disadvantages, as #1805 mentions.
(Fewer unneeded options to choose from also simplifies
the work of coaches and of those maintaining the tutorial.)

Also, completely remove the special case for RunCode users
in the "Python prompt" section, as at that point,
they've already been told to follow Linux instructions.

fixes #1805

Author: das-g

en/cloud_development_setup/instructions.md

@@ -15,8 +15,6 @@ which you can sign up with.
 ## Command Line
 To open the Ubuntu terminal on RunCode, go to Workspaces → New Workspace → Blank. This will open a new Visual Studio Code workspace which has an Ubuntu terminal in the bottom pane.
 
-Altenatively, you can go to Workspaces → New Workspace → Jupyter Lab. This will open a Python prompt which is depicted by `>>>`, you can type `exit()` to get back to the Ubuntu terminal.
-
 Ubuntu is a version of Linux so for all command line instructions later in the tutorial you can follow Linux instructions.
 
 ## Virtual Environment

en/intro_to_command_line/open_instructions.md

@@ -31,8 +31,6 @@ It's probably under Applications → Accessories → Terminal, or Applications 
 
 To open the Ubuntu terminal on RunCode, go to Workspaces → New Workspace → Blank. This will open a new Visual Studio Code workspace which has an Ubuntu terminal in the bottom pane.
 
-Altenatively, you can go to Workspaces → New Workspace → Jupyter Lab. This will open a Python prompt which is depicted by `>>>`, you can type `exit()` to get back to the Ubuntu terminal.
-
 Ubuntu is a version of Linux so from now on you can follow Linux instructions.
 
 <!--endsec-->

en/python_introduction/prompt.md

@@ -15,12 +15,3 @@ Python {{ book.py_release }} (...)
 Type "help", "copyright", "credits" or "license" for more information.
 >>>
 ```
-
-<!--sec data-title="Opening: RunCode Cloud Environment" data-id="runcode_prompt" data-collapse=true ces-->
-
-To open the Python terminal on RunCode, go to Workspaces → New Workspace → Jupyter Lab. This will open a Python prompt 
-which is depicted by `>>>`. If you already opened an Ubuntu terminal open, in the [Intro to Command Line](../intro_to_command_line/README.md) chapter, you can just type `python3` in the prompt as shown below to open a Python prompt.
-
-`ubuntu@runcode:~$ python3`
-
-<!--endsec-->