ex_weno_nanovdb_cpu: remove stray emacs lock symlink

.#weno_nanovdb_cpu.cpp is an emacs per-user lock artifact that got
swept up by `git add` in the previous commit.  It's a dangling symlink
to esifakis@host:pid, not a meaningful repo artifact.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Efty Sifakis <esifakis@nvidia.com>

Author: sifakis