Studio: bump sentence-transformers pin for multimodal RAG (BGE-VL)

BGE-VL's custom modeling code imports
sentence_transformers.base.modules.transformer, which doesn't exist
in the 5.2.0 pin. Bump to >=5.3.0,<7 so the new Module package is
available.

studio/backend/requirements/extras-no-deps.txt

@@ -14,7 +14,10 @@ trl==0.23.1
 git+https://github.com/meta-pytorch/OpenEnv.git
 # executorch>=1.0.1               # 41.5 MB - no imports in unsloth/zoo/studio
 torch-c-dlpack-ext
-sentence_transformers==5.2.0
+# Bumped from 5.2.0 to pick up the `sentence_transformers.base.modules`
+# package that BGE-VL's custom modeling code imports for multimodal RAG.
+# Upper bound left at <7 so a future major rewrite doesn't auto-resolve.
+sentence_transformers>=5.3.0,<7
 transformers==4.57.6
 pytorch_tokenizers
 kernels==0.12.1