More rubocop fixes

Author: vipulnsward

lib/uploadcare/param/authentication_header.rb

@@ -23,15 +23,19 @@ def self.call(options = {})
       end
 
       def self.validate_auth_config
-        raise Uploadcare::Exception::AuthError, 'Public Key is blank.' if is_blank?(Uploadcare.config.public_key)
-        raise Uploadcare::Exception::AuthError, 'Secret Key is blank.' if is_blank?(Uploadcare.config.secret_key)
+        if empty_config_for?(Uploadcare.config.public_key)
+          raise Uploadcare::Exception::AuthError,
+                'Public Key is blank.'
+        end
+        return unless empty_config_for?(Uploadcare.config.secret_key)
+
+        raise Uploadcare::Exception::AuthError,
+              'Secret Key is blank.'
       end
 
-      # rubocop:disable Naming/PredicateName
-      def self.is_blank?(value)
+      def self.empty_config_for?(value)
         value.nil? || value.empty?
       end
-      # rubocop:enable Naming/PredicateName
     end
   end
 end