The previous output had a trailing backslash on the last hash line;
while this is apparently valid for both pip-sync and pip install, IMHO
it looks like a bug, and it also doesn’t reflect what pip-compile
currently emits (as of version 6.12.3), so update the example.

This puts the hashes example out of sync with some of the other examples
in the README, but they weren’t all in sync before either (various
examples were already referencing Django 4, 3 or 2), so I hope that’s
not an issue.

In one case (layered requirements), I had to add a constraint on the
django-debug-toolbar version because otherwise no solution was found by
the legacy resolver. (The backtracking resolver does find a solution,
but isn’t the default yet.) This should probably be revisited later,
ideally by someone more knowledgeable than me :)