Used implicit type assignment for variable

When I moved the `SqlCommand` assignments outside of the `try/catch` blocks (see #8590d46), that opened up the ability to use implicit typing for variables. (Technically, that could have been done previously—and, in fact, was for other cases; but it definitely makes more sense now that the values aren't being initialized to `null`.)

Author: JeremyCaney

OnTopic.Data.Sql/SqlTopicRepository.cs

@@ -495,7 +495,7 @@ public override void Delete(Topic topic, bool isRecursive = false) {
       | Delete from database
       \-----------------------------------------------------------------------------------------------------------------------*/
       var connection            = new SqlConnection(_connectionString);
-      SqlCommand? command       = new SqlCommand("DeleteTopic", connection) {
+      var command               = new SqlCommand("DeleteTopic", connection) {
         CommandType             = CommandType.StoredProcedure
       };