chore: removing unused clone_depth from appveyor.yaml

according to their docs (https://www.appveyor.com/docs/how-to/repository-shallow-clone/)
"If both clone_depth and shallow_clone exist in the config, clone_depth is ignored."
we're apparently mentioning both, so clone_depth is ignored - might as well remove it.

appveyor.yml

@@ -10,7 +10,6 @@ init:
   - git config --global core.autocrlf true
 
 shallow_clone: true
-clone_depth: 1
 
 cache:
   - node_modules -> package.json