schema: add SVS-VAMANA to index_types enum

SVS-VAMANA is a vector index type introduced in Redis 8.2. Adding it
to the allowed enum to unblock PR #589.

Author: svonava

docs/tools/vdb_table/vendor.schema.json

@@ -132,6 +132,7 @@
               "MSTG",
               "FAISS-IVF",
               "Tree-AH",
+              "SVS-VAMANA",
               "Proprietary",
               "not known"
             ]