appveyor: Fix python PATH for a new pywin32-309.

Pip is unable to install new pywin32 v309 with the following warning:

  WARNING: The scripts pywin32_postinstall.exe and pywin32_testall.exe
  are installed in 'C:\Python312-x64\Scripts' which is not on PATH.

This now fails all the windows builds.

It looks like this directory is generally required for pip and some
other packages to work properly, we just didn't hit the issue until
it became required for pywin32.

Let's add it to the PATH.

Acked-by: Alin Gabriel Serdean <aserdean@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Author: igsilya

appveyor.yml

@@ -10,7 +10,7 @@ clone_folder: C:\openvswitch_compile
 shallow_clone: true
 
 init:
-- ps: $env:PATH ="C:\Python312-x64;"+$env:PATH
+- ps: $env:PATH ="C:\Python312-x64;C:\Python312-x64\Scripts;"+$env:PATH
 - ps: New-Item -Type HardLink -Path  "C:\Python312-x64\python3.exe"
                               -Value "C:\Python312-x64\python.exe"