Console: Reuse iterator in unregisterCommand()
Console: Reuse iterator in unregisterCommand()

We can use the result of the first lookup to avoid doing another
redundant lookup to perform the erasure.

While we're at it, we can use std::string's std::string_view constructor
in order to avoid an unnecessary strlen() call.

RetroView/hecl,RetroView/hecl,RetroView/hecl,RetroView/hecl