False positive when using re-assigned query variable

```go
f6 := `UPDATE * FROM test WHERE test=?`
_, _ = db.Exec(f6, s)

// re-assign variable f6
f6 = `SELECT * FROM test WHERE test=?`
_ = db.QueryRow(f6, s)
```

The above snippet produces the following error on the last line:

```Use Exec instead of QueryRow to execute `UPDATE` query```