Update appveyor.yml

Author: genius257

appveyor.yml

@@ -10,7 +10,7 @@ branches:
 cache:
   - au3pm -> **\au3pm.json, **\au3pm.lock
 install:
-  - ps: (new-object net.webclient).DownloadFile('https://github.com/genius257/au3pm/releases/download/1/au3pm.exe', 'au3pm.exe')
+  - ps: (new-object net.webclient).DownloadFile('https://github.com/genius257/au3pm/releases/latest/download/au3pm.exe', 'au3pm.exe')
   - ps: au3pm install
 build_script:
   - au3pm build