Fixed a couple of comments

Author: shift-evgeny

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -463,7 +463,7 @@ public virtual SqlExpression<T> GroupBy<TKey>(Expression<Func<T, TKey>> keySelec
             useFieldName = true;
 
             var groupByKey = Visit(keySelector);
-            StripAliases(groupByKey as SelectList); // No "AS ColumnAlias" in GROUP BY, just the column names
+            StripAliases(groupByKey as SelectList); // No "AS ColumnAlias" in GROUP BY, just the column names/expressions
 
             return GroupBy(groupByKey.ToString());
         }

tests/ServiceStack.OrmLite.Tests/Expression/SqlExpressionTests.cs

@@ -83,7 +83,7 @@ public void Can_select_Dictionary_with_SqlExpression()
                 var map = db.Dictionary<string, int>(query);
                 Assert.That(map.EquivalentTo(expected));
 
-                // Same, but group by an anonymous type using an alias -t his should not translate to "GROUP BY TheLetter AS Letter", which is invalid SQL
+                // Same, but group by an anonymous type using an alias - this should not translate to "GROUP BY TheLetter AS Letter", which is invalid SQL
 
                 query = db.From<LetterFrequency>()
                   .Select(x => new { x.Letter, count = Sql.Count("*") })