Remove codespaces setup

Author: cpq

README.md

@@ -75,22 +75,6 @@ $ sudo apt -y install gcc-arm-none-eabi make stlink-tools
   arm-none-eabi-gcc main.c  -W -Wall -Wextra -Werror ...
   </pre>
 
-### Setup instruction for in-browser development (using GitHub Codespaces):
-
-- Click on the "Code" button, select "Codespaces" tab, click on plus icon
-  <img src="images/codespace.png" width="50%" />
-- This repository will be opened in the in-browser editor, with an opened terminal:
-  <img src="images/codespace-terminal.png" width="75%" />
-- Execute Linux/Ubuntu setup instructions in the terminal:
-  ```sh
-  sudo apt -y update
-  sudo apt -y install gcc-arm-none-eabi make stlink-tools
-  ```
-- Verify that the build process works:
-  ```sh
-  cd step-4-printf
-  make firmware.bin
-  ```
 
 ## Introduction