Remove node.js v11 no longer maintained

Maintenance of Node.js v11 ended 2019-06-01
https://github.com/nodejs/Release/blob/f4ae92f443f57f4b8f0716859a9a64ba055caac4/schedule.json#L56

Author: tvainika

.travis.yml

@@ -142,27 +142,6 @@ jobs:
         - NODE_VERSION="10"
         - VARIANT="stretch-slim"
 
-    - stage: Build
-      before_script: *auto_skip
-      name: 11 on alpine
-      env:
-        - NODE_VERSION="11"
-        - VARIANT="alpine"
-
-    - stage: Build
-      before_script: *auto_skip
-      name: 11 on stretch
-      env:
-        - NODE_VERSION="11"
-        - VARIANT="stretch"
-
-    - stage: Build
-      before_script: *auto_skip
-      name: 11 on stretch-slim
-      env:
-        - NODE_VERSION="11"
-        - VARIANT="stretch-slim"
-
     - stage: Build
       before_script: *auto_skip
       name: 12 on alpine

11/alpine/Dockerfile

@@ -11,8 +11,6 @@ array_8='8 carbon'
 # shellcheck disable=SC2034
 array_10='10 dubnium lts'
 # shellcheck disable=SC2034
-array_11='11'
-# shellcheck disable=SC2034
 array_12='12 current latest'
 # shellcheck disable=SC2034
 array_chakracore_8='chakracore-8'