Fix column `NULL`ness for OrganizationUser table (#1239)

Fix column `NULL`ness for OrganizationUser table in Upgrade script; prior PR I missed in the upgrade script submitted that the ALTER COLUMN statement incorrectly set the column to `NOT NULL` when the table definition had it correctly as `NULL`.

util/Migrator/DbScripts/2021-03-04_03_OrganizationUser_Enlarge_Email_Column.sql

@@ -3,7 +3,7 @@ IF COL_LENGTH('[dbo].[OrganizationUser]', 'Email') = 100
 BEGIN
 	ALTER TABLE [dbo].[OrganizationUser] 
 	ALTER COLUMN 
-		Email NVARCHAR(256) NOT NULL
+		Email NVARCHAR(256) NULL
 END
 GO
 
@@ -301,4 +301,4 @@ BEGIN
             OR (@OnlyUsers = 1 AND U.[Email] = @Email)
         )
 END
-GO
+GO