fix: pin huggingface_hub<0.16 for sentence-transformers 2.2.2 compatibility

sentence-transformers==2.2.2 imports cached_download from huggingface_hub,
which was removed in huggingface_hub 0.26. Fresh builds have been failing
at get_vectors.py import time since late 2024; this pin restores the
previously-working dependency set.

Verified end-to-end with docker build --no-cache and the bundled
tests/data/ sample: the full pipeline embeds, aligns, and produces
non-empty .train_cleaned output.

Author: evanyerburgh

requirements.txt

@@ -1,3 +1,4 @@
 sentence-transformers==2.2.2
 pyewts==0.2.0
 Cython==0.29.34
+huggingface_hub<0.16