bug#33998: 27.0.50; cl-delete does not delete the first list element

[Drew Adams]

> So, cumbersome as it is, you should always use:
                               ^^^^^^^^^^^^^
> (setq seq (cl-delete thing seq))

FWIW, this is not really true.

`cl-delete' deletes THING from the
_value_ of SEQ.  You might or you
might not want variable SEQ to have
the updated value.  A variable and
its value are two different things.

IOW, that's one common, and important,
use case, but this is not some
always-do-this rule for users.

The manual takes pains to explain
this stuff carefully.  It's better
to just refer to the manual to help
users understand it.  (And you did
that, which is great.)