ci: use windows-latest instead of deprecated windows-2019

Author: madebr

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         platform:
-        - { name: Windows (MSVC),       os: windows-2019, shell: sh,   cmake: '-DPerl_ROOT=C:/Strawberry/perl/bin/ -DSDLMIXER_VENDORED=ON -GNinja', msvc: 1, shared: 1, static: 0, artifact: 'SDL3_mixer-VC-x64' }
+        - { name: Windows (MSVC),       os: windows-latest, shell: sh,   cmake: '-DPerl_ROOT=C:/Strawberry/perl/bin/ -DSDLMIXER_VENDORED=ON -GNinja', msvc: 1, shared: 1, static: 0, artifact: 'SDL3_mixer-VC-x64' }
         - { name: Windows (mingw64),    os: windows-latest, shell: 'msys2 {0}', msystem: mingw64, msys-env: mingw-w64-x86_64, shared: 1, static: 0, artifact: 'SDL3_mixer-mingw64',
             cmake: '-DSDLMIXER_VENDORED=OFF -G "Ninja Multi-Config"' }
         - { name: Linux,                os: ubuntu-latest, shell: sh, cmake: '-DSDLMIXER_VENDORED=ON -GNinja', shared: 1, static: 0, artifact: 'SDL3_mixer-linux-x64' }