Avoid warning when creating new databases

When creating a new database we execute a couple of SQL statements after
opening the new file. However, since none of them happen in a
transaction there's no need to commit them. This change gets rid of the
commit statement and avoids a warning being printed by doing so.

See issue #583.

src/sqlitedb.cpp

@@ -396,7 +396,6 @@ bool DBBrowserDB::create ( const QString & db)
             NoStructureUpdateChecks nup(*this);
             executeSQL("CREATE TABLE notempty (id integer primary key);", false, false);
             executeSQL("DROP TABLE notempty;", false, false);
-            executeSQL("COMMIT;", false, false);
         }
 
         // Execute default SQL