windows: use specific python3.9.exe

docker/install-scrypted-dependencies-win.ps1

@@ -12,6 +12,7 @@ choco upgrade -y nodejs-lts --version=18.14.0
 
 # Install Python
 choco upgrade -y python39
+$SCRYPTED_PYTHON_PATH = (get-command python3.9.exe).Path
 
 # Refresh environment variables for py and npx to work
 $env:Path = [System.Environment]::GetEnvironmentVariable("Path","Machine") + ";" + [System.Environment]::GetEnvironmentVariable("Path","User") 
@@ -59,7 +60,7 @@ const svc = new Service({
     },
     {
       name: "SCRYPTED_PYTHON_PATH",
-      value: "python3.9.exe",
+      value: "$($SCRYPTED_PYTHON_PATH)",
     }
   ]
 });