removed VS15 from CI

.gitlab-ci.yml

@@ -18,20 +18,6 @@ VS2017-x64:
     paths:
       - "*/*-build/Release/*.exe"
 
-VS2015-x64:
-  stage:
-    Build
-  script: "CI\\ci-windows-build.bat"
-  variables:
-     GIT_SUBMODULE_STRATEGY: recursive
-     ARCHITECTURE: "x64"
-     COMPILER: "VS2015"
-  tags: 
-    - VS2015
-  artifacts:
-    paths:
-      - "*/*-build/Release/*.exe"
-
 gcc:
   stage: Build
   script: "CI/ci-linux.sh gcc"