fix unresolved package requirement to install Humble on Ubuntu 20.04 (r…

…os2#3086)

* fix command to install humble on Ubuntu 20.04

Co-authored-by: paolo.dimasi <paodimasi@outlook.com>
Co-authored-by: Chris Lalancette <clalancette@openrobotics.org>

source/Installation/Alternatives/Ubuntu-Development-Setup.rst

@@ -46,6 +46,8 @@ Add the ROS 2 apt repository
 Install development tools and ROS tools
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Install common packages
+
 .. code-block:: bash
 
    sudo apt update && sudo apt install -y \
@@ -54,24 +56,50 @@ Install development tools and ROS tools
      git \
      python3-colcon-common-extensions \
      python3-flake8 \
-     python3-flake8-blind-except \
-     python3-flake8-builtins \
-     python3-flake8-class-newline \
-     python3-flake8-comprehensions \
-     python3-flake8-deprecated \
      python3-flake8-docstrings \
-     python3-flake8-import-order \
-     python3-flake8-quotes \
      python3-pip \
      python3-pytest \
      python3-pytest-cov \
-     python3-pytest-repeat \
-     python3-pytest-rerunfailures \
      python3-rosdep \
      python3-setuptools \
      python3-vcstool \
      wget
 
+Install packages according to your Ubuntu version
+
+.. tabs::
+
+   .. group-tab:: Ubuntu 22.04 LTS and later
+
+      .. code-block:: console
+
+         sudo apt install -y \
+            python3-flake8-blind-except
+            python3-flake8-builtins
+            python3-flake8-class-newline
+            python3-flake8-comprehensions
+            python3-flake8-deprecated
+            python3-flake8-import-order
+            python3-flake8-quotes
+            python3-pytest-repeat
+            python3-pytest-rerunfailures
+
+   .. group-tab:: Ubuntu 20.04 LTS
+
+      .. code-block:: bash
+
+         python3 -m pip install -U \
+            flake8-blind-except \
+            flake8-builtins \
+            flake8-class-newline \
+            flake8-comprehensions \
+            flake8-deprecated \
+            flake8-import-order \
+            flake8-quotes \
+            pytest-repeat \
+            pytest-rerunfailures
+
+
 .. _linux-dev-get-ros2-code:
 
 Get ROS 2 code