Update to Drone 1.x compatible matrix config

.drone.yml

@@ -1,21 +1,18 @@
 pipeline:
   build:
     image: spritsail/docker-build
-    volumes: [ '/var/run/docker.sock:/var/run/docker.sock' ]
     repo: alpine-dev
     build_args:
       - ALPINE_TAG=${ALPINE_TAG%%,*}
 
   test:
     image: spritsail/docker-test
-    volumes: [ '/var/run/docker.sock:/var/run/docker.sock' ]
     repo: alpine-dev
     run: su-exec nobody apk --version
 
   publish:
     image: spritsail/docker-publish
     when: { branch: [ master ], event: [ push, tag, deployment ] }
-    volumes: [ '/var/run/docker.sock:/var/run/docker.sock' ]
     secrets: [ docker_username, docker_password ]
     from: alpine-dev
     repo: 'spritsail/alpine'
@@ -29,7 +26,6 @@ pipeline:
 
 matrix:
   ALPINE_TAG:
-    - 3.7
     - 3.8
     - 3.9
     - 3.10,latest