Update supported platforms; discontinue Ubuntu 16 and openSUSE 15

builder/docker-compose.yml

@@ -1,17 +1,6 @@
 version: '2.0'
 
 services:
-  ubuntu-1604:
-    command: ./build.sh
-    environment:
-      - R_VERSION=${R_VERSION}
-      - LOCAL_STORE=/tmp/output
-    build:
-      context: .
-      dockerfile: Dockerfile.ubuntu-1604
-    image: r-builds:ubuntu-1604
-    volumes:
-      - ./integration/tmp:/tmp/output
   ubuntu-1804:
     command: ./build.sh
     environment:
@@ -100,17 +89,6 @@ services:
     image: r-builds:opensuse-42
     volumes:
       - ./integration/tmp:/tmp/output
-  opensuse-15:
-    command: ./build.sh
-    environment:
-      - R_VERSION=${R_VERSION}
-      - LOCAL_STORE=/tmp/output
-    build:
-      context: .
-      dockerfile: Dockerfile.opensuse-15
-    image: r-builds:opensuse-15
-    volumes:
-      - ./integration/tmp:/tmp/output
   opensuse-152:
     command: ./build.sh
     environment: