Revert "Use node 14 on appveyor"
Revert "Use node 14 on appveyor"

This reverts commit f725ff05f4738c43a6b9089a41a50478f56f5092.

codarchlab/idai-field-client,codarchlab/idai-field-client,codarchlab/idai-field-client,codarchlab/idai-field-client