Update variables-transact-sql.md

Corrected example incorrectly showing two batches of statements separated by GO. This change shows code that accurately reflects the point being made in the section.

Author: athomas-octoberthree

docs/t-sql/language-elements/variables-transact-sql.md

@@ -75,6 +75,7 @@ GO
 
 DECLARE @MyVariable AS INT;
 SET @MyVariable = 1;
+GO
 
 SELECT BusinessEntityID,
        NationalIDNumber,