Changed Python 3.9 job to use Windows Server 2016

.appveyor.yml

@@ -21,12 +21,14 @@ environment:
   - PYTHON: C:/Python312
     ARCHITECTURE: x86
     APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
-  - PYTHON: C:/Python39-x64
+  - PYTHON: C:/Python39
+    CHOCO_PYTHON_VERSION: 3.9.13
     ARCHITECTURE: AMD64
-    APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
 
 
 install:
+- if not exist '%PYTHON%' choco install python --version=%CHOCO_PYTHON_VERSION%
 - '%PYTHON%\%EXECUTABLE% --version'
 - '%PYTHON%\%EXECUTABLE% -m pip install --upgrade pip'
 - curl -fsSL -o pillow-test-images.zip https://github.com/python-pillow/test-images/archive/main.zip

docs/installation/platform-support.rst

@@ -48,7 +48,7 @@ These platforms are built and tested for every change.
 | Ubuntu Linux 24.04 LTS (Noble)   | 3.12                       | x86-64, ppc64le,    |
 |                                  |                            | s390x               |
 +----------------------------------+----------------------------+---------------------+
-| Windows Server 2019              | 3.9                        | x86-64              |
+| Windows Server 2016              | 3.9                        | x86-64              |
 +----------------------------------+----------------------------+---------------------+
 | Windows Server 2022              | 3.9, 3.10, 3.11,           | x86-64              |
 |                                  | 3.12, 3.13, PyPy3          |                     |

winbuild/README.md

@@ -11,7 +11,7 @@ For more extensive info, see the [Windows build instructions](build.rst).
 * Requires Microsoft Visual Studio 2017 or newer with C++ component.
 * Requires NASM for libjpeg-turbo, a required dependency when using this script.
 * Requires CMake 3.15 or newer (available as Visual Studio component).
-* Tested on Windows Server 2019 with Visual Studio 2019 Community and Visual Studio 2022 Community (AppVeyor).
+* Tested on Windows Server 2016 with Visual Studio 2017 Community, and Windows Server 2019 with Visual Studio 2022 Community (AppVeyor).
 * Tested on Windows Server 2022 with Visual Studio 2022 Enterprise (GitHub Actions).
 
 The following is a simplified version of the script used on AppVeyor: