AppVeyor: Drop "clone_depth: 1" because subsequent pushes were failing ongoing builds
Symptom:
Build started
git config --global core.autocrlf input
git clone -q --depth=1 --branch=master https://github.com/libexpat/libexpat.git c:\projects\libexpat
git checkout -qf
d4d8d486af1810bff52612d84533985b9b47b7a6
fatal: reference is not a tree:
d4d8d486af1810bff52612d84533985b9b47b7a6
Cause:
A more recent push made
d4d8d486af1810bff52612d84533985b9b47b7a6
the second-last commit so that --depth=1 would create a commit
graph without that commit.
Documented at:
https://www.appveyor.com/docs/how-to/repository-shallow-clone/#setting-depth-of-git-clone-command