Merge bitcoin/bitcoin#22247: Switch Appveyor CI to VS2019 stable image

aab7fd0 Switch Appveyor CI to VS2019 stable image (Aaron Clauson)

Pull request description:

  The current appveyor config is using the VS2019 preview image so the latest prebuilt Qt5.12.11 binaries can be used, see #22224.

  Appveyor updated the Visual Studio 2019 image to msbuild v16.10.1 on 14th of June. This is the version used to build the latest Qt binaries and removes the need to use the Appveyor VS2019 preview image.

ACKs for top commit:
  MarcoFalke:
    review ACK aab7fd0 if green
  practicalswift:
    cr ACK aab7fd0: patch looks correct
  hebasto:
    ACK aab7fd0

Tree-SHA512: 42ea4e6e27a2099ddeed99a3352e8ff014df1e93fbcb1f0f2ebd6f22ec2fb71212275a2adb2a7858516203e566c6ba053367b4ac7e0b74457f7a35e941d6fdd4

.appveyor.yml

@@ -1,6 +1,6 @@
 version: '{branch}.{build}'
 skip_tags: true
-image: Visual Studio 2019 Preview
+image: Visual Studio 2019
 configuration: Release
 platform: x64
 clone_depth: 5