refactor(b038): Cleanup unused code in B038Checker

[mimre25]

The unused code would introduce a bug when used, thus I believe it's better to remove it.

Essentially, it would've flagged any del statement within a loop, without check for the name.
However, because the B038Checker visits Del nodes, and doesn't call generic_visit from there, we'll never reach a Name node that has the ctx == Del.

I've added a test case, just to make sure 🙂

[cooperlees]

Awesome. Thanks for finding before it went wide and we got flooded with false positives!