Remove Bionic from future releases (Garden+) (#371)

Signed-off-by: Louise Poubel <louise@openrobotics.org>

.github/workflows/ci.yml

@@ -3,18 +3,6 @@ name: Ubuntu CI
 on: [push, pull_request]
 
 jobs:
-  bionic-ci:
-    runs-on: ubuntu-latest
-    name: Ubuntu Bionic CI
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: Compile and test
-        id: ci
-        uses: ignition-tooling/action-ignition-ci@bionic
-        with:
-          codecov-enabled: true
-          doxygen-enabled: true
   focal-ci:
     runs-on: ubuntu-latest
     name: Ubuntu Focal CI
@@ -24,3 +12,8 @@ jobs:
       - name: Compile and test
         id: ci
         uses: ignition-tooling/action-ignition-ci@focal
+        with:
+          codecov-enabled: true
+          cppcheck-enabled: true
+          cpplint-enabled: true
+          doxygen-enabled: true

README.md

@@ -10,7 +10,7 @@
 Build | Status
 -- | --
 Test coverage | [![codecov](https://codecov.io/gh/ignitionrobotics/ign-gui/branch/main/graph/badge.svg)](https://codecov.io/gh/ignitionrobotics/ign-gui/branch/main)
-Ubuntu Bionic | [![Build Status](https://build.osrfoundation.org/buildStatus/icon?job=ignition_gui-ci-main-bionic-amd64)](https://build.osrfoundation.org/job/ignition_gui-ci-main-bionic-amd64)
+Ubuntu Focal | [![Build Status](https://build.osrfoundation.org/buildStatus/icon?job=ignition_gui-ci-main-focal-amd64)](https://build.osrfoundation.org/job/ignition_gui-ci-main-focal-amd64)
 Homebrew      | [![Build Status](https://build.osrfoundation.org/buildStatus/icon?job=ignition_gui-ci-main-homebrew-amd64)](https://build.osrfoundation.org/job/ignition_gui-ci-main-homebrew-amd64)
 Windows       | [![Build Status](https://build.osrfoundation.org/buildStatus/icon?job=ign_gui-ci-win)](https://build.osrfoundation.org/job/ign_gui-ci-win)
 

tutorials/01_install.md

@@ -58,7 +58,7 @@ Binary install is pending `ignition-rendering` and `ignition-gui` being added to
 
 ## Source Install
 
-### Ubuntu Bionic 18.04 or above
+### Ubuntu Focal 20.04 or above
 
 #### Install Prerequisites
 
@@ -82,11 +82,6 @@ Install dependencies
   sudo apt -y install $(sort -u $(find . -iname 'packages.apt') | tr '\n' ' ')
   ```
 
-Only on Bionic, update the GCC compiler version:
-  ```
-  sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 800 --slave /usr/bin/g++ g++ /usr/bin/g++-8 --slave /usr/bin/gcov gcov /usr/bin/gcov-8
-  ```
-
 #### Build from source
 
 Build and install as follows: