Remove methods deprecated and turned off February 2021.

Author: dblock

lib/tasks/web.rake

@@ -32,6 +32,7 @@ namespace :slack do
           parsed = JSON.parse(File.read(path))
           parsed['undocumented'] = true if path =~ /undocumented/
           JSON::Validator.validate(method_schema, parsed, insert_defaults: true)
+          next if parsed['deprecated'] && parsed['deprecation']['deprecation_warning'] =~ /It will stop functioning in February 2021/
           result[prefix][name] = parsed
         end