[CI] Remove Windows 2016 testing (elastic#121941) (elastic#121956)

(cherry picked from commit b952809)

Author: brianseeders

.buildkite/pipelines/periodic-packaging.template.yml

@@ -43,7 +43,6 @@ steps:
         matrix:
           setup:
             image:
-              - windows-2016
               - windows-2019
               - windows-2022
         agents:

.buildkite/pipelines/periodic-packaging.yml

@@ -636,7 +636,6 @@ steps:
         matrix:
           setup:
             image:
-              - windows-2016
               - windows-2019
               - windows-2022
         agents:

.buildkite/pipelines/periodic-platform-support.yml

@@ -42,7 +42,6 @@ steps:
         matrix:
           setup:
             image:
-              - windows-2016
               - windows-2019
               - windows-2022
             GRADLE_TASK:

.buildkite/pipelines/pull-request/packaging-tests-windows.yml

@@ -10,7 +10,6 @@ steps:
         matrix:
           setup:
             image:
-              - windows-2016
               - windows-2019
               - windows-2022
             PACKAGING_TASK: