Update Azure CI to not use ubuntu-16.04 images

Signed-off-by: Ayan Sinha Mahapatra <ayansmahapatra@gmail.com>

Author: AyanSinhaMahapatra

azure-pipelines.yml

@@ -13,7 +13,7 @@ jobs:
     - template: etc/ci/azure-posix.yml
       parameters:
           job_name: core_tests
-          image_name: ubuntu-16.04
+          image_name: ubuntu-20.04
           python_versions: ['3.6']
           test_suites:
               misc: |
@@ -144,15 +144,6 @@ jobs:
           test_suites:
               all: Scripts\pytest -n 2 -vvs tests\scancode\test_cli.py
 
-    - template: etc/ci/azure-posix.yml
-      parameters:
-          job_name: ubuntu16
-          image_name: ubuntu-16.04
-          python_versions: ['3.7', '3.8', '3.9']
-          python_architecture: x64
-          test_suites:
-              all: bin/pytest -n 2 -vvs tests/scancode/test_cli.py
-
 
     - template: etc/ci/azure-posix.yml
       parameters:
@@ -301,7 +292,7 @@ jobs:
 #
 #    - job: Build_release_archive_py3
 #      pool:
-#          vmImage: ubuntu-16.04
+#          vmImage: ubuntu-18.04
 #      steps:
 #          - checkout: self
 #            fetchDepth: 10