Update sentence_bert_config.json

Align the `sentence_bert_config.json` with the `max_position_embeddings` defined in `config.json`.

sentence_bert_config.json

@@ -1,4 +1,4 @@
 {
-  "max_seq_length": 256,
+  "max_seq_length": 32768,
   "do_lower_case": false
 }