migrate from deprecated ubuntu-16.04 vmImage

azure-pipelines.yml

@@ -19,7 +19,7 @@ jobs:
 # of gcc / glibc
 - job: manylinux1_gcc
   pool:
-    vmImage: 'ubuntu-16.04'
+    vmImage: 'ubuntu-latest'
   steps:
   - script: |
       echo "FROM quay.io/pypa/manylinux1_x86_64
@@ -35,7 +35,7 @@ jobs:
     displayName: Run manylinux1 docker build
 - job: Intel_SDE_skx
   pool:
-    vmImage: 'ubuntu-16.04'
+    vmImage: 'ubuntu-latest'
   steps:
   - script: |
       # at the time of writing the available Azure Ubuntu vm image