Improved example [skip ci]

Author: ankane

examples/sentence_transformers/example.py

@@ -10,7 +10,7 @@
 conn.execute('DROP TABLE IF EXISTS documents')
 conn.execute('CREATE TABLE documents (id bigserial PRIMARY KEY, content text, embedding vector(384))')
 
-model = SentenceTransformer('all-MiniLM-L6-v2')
+model = SentenceTransformer('multi-qa-MiniLM-L6-cos-v1')
 
 input = [
     'The dog is barking',