drop the stray libwebsockets gitlink

There is no .gitmodules, so this was never a submodule: it is a bare
mode 160000 entry left behind by committing a nested lws clone, which
git can only report as a modified submodule with no mapping.  Nothing in
the build refers to it -- we build against the installed lws -- so drop
the entry and ignore the path, so a working lws checkout there stays out
of the way instead of showing up as a pending change.

The checkout itself is left alone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>