SpacyProcessor latest version requires a different type for config field `processors`

[jennyzhang-petuum]

To solve the version mismatch of latest forte-wrappers and this repo, which is that SpacyProcessor latest version requires a list of string rather than string for config field processors, we need to make modifications of this repo.
L20 and L25 need to be changed to list of string in the file below.
config.yml