fix: remove default value for longtext type

Author: arrabito

src/DIRAC/ProductionSystem/DB/ProductionDB.sql

@@ -44,8 +44,8 @@ CREATE TABLE ProductionSteps(
     Plugin CHAR(32) DEFAULT 'None',
     AgentType CHAR(32) DEFAULT 'Manual',
     GroupSize INT NOT NULL DEFAULT 1,
-    InputQuery LONGTEXT DEFAULT 'None',
-    OutputQuery LONGTEXT DEFAULT 'None',
+    InputQuery LONGTEXT,
+    OutputQuery LONGTEXT,
     LastUpdate DATETIME,
     InsertedTime DATETIME,
     PRIMARY KEY(StepID),