appveyor: remove

It's slow and currently broken because it hasn't been updated in the last month.

README.md

@@ -5,8 +5,6 @@
   -->
   <a title="GitHub Actions" href="https://github.com/msys2/MINGW-packages/actions?query=workflow%3Amain"><img alt="'main' workflow Status" src="https://img.shields.io/github/workflow/status/msys2/MINGW-packages/main?longCache=true&style=flat-square&label=build&logo=github"></a><!--
   -->
-  <a title="AppVeyor" href="https://ci.appveyor.com/project/Alexpux/mingw-packages"><img src="https://img.shields.io/appveyor/ci/Alexpux/mingw-packages/master.svg?logo=appveyor&logoColor=e8ecef&style=flat-square"></a><!--
-  -->
 </p>
 
 # MINGW-packages

appveyor.yml

@@ -1,37 +0,0 @@
-clone_folder: C:\M
-
-environment:
-    PATH: C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Program Files\Git\cmd
-    DEPLOY_PROVIDER: bintray
-    BINTRAY_ACCOUNT: alexpux
-    BINTRAY_REPOSITORY: msys2
-    PACMAN_REPOSITORY_NAME: ci.mingw
-    BUILD_URL: https://ci.appveyor.com/project/$(APPVEYOR_ACCOUNT_NAME)/$(APPVEYOR_PROJECT_NAME)/build/$(APPVEYOR_BUILD_VERSION)
-    matrix:
-        - MINGW_INSTALLS: mingw32
-        - MINGW_INSTALLS: mingw64
-
-matrix:
-    fast_finish: true
-
-build_script:
-    - rmdir /s /Q C:\OpenSSL-Win32 C:\OpenSSL-Win64
-    - C:\msys64\usr\bin\pacman --noconfirm --ask 20 --sync --refresh --refresh --sysupgrade --sysupgrade
-    - C:\msys64\usr\bin\bash --login -c "$(cygpath ${APPVEYOR_BUILD_FOLDER})/ci-build.sh"
-
-test: off
-
-artifacts:
-    - path: artifacts\*
-
-deploy:
-    - provider: BinTray
-      username: $(BINTRAY_ACCOUNT)
-      subject: $(BINTRAY_ACCOUNT)
-      repo: $(BINTRAY_REPOSITORY)
-      package: $(PACMAN_REPOSITORY_NAME)
-      version: latest
-      publish: true
-      override: true
-      api_key:
-          secure: B2XBLbsX8EQOpWyyaHskipMoF2+Tbt6hc/afbVm82f01CBKruspjwhee4K4C7/xf