fix(documet):upgrade document updatetime when upgrade document_char_length (#3211)

fixed #2942

Author: liuchangfitcloud

apps/dataset/sql/update_document_char_length.sql

@@ -2,6 +2,7 @@ UPDATE "document"
 SET "char_length" = ( SELECT CASE WHEN
 		"sum" ( "char_length" ( "content" ) ) IS NULL THEN
 			0 ELSE "sum" ( "char_length" ( "content" ) )
-		END FROM paragraph WHERE "document_id" = %s )
+		END FROM paragraph WHERE "document_id" = %s ),
+    "update_time" = CURRENT_TIMESTAMP
 WHERE
 	"id" = %s