enable 3 char words to finegrind tokenize (#2210)

### What problem does this PR solve?


### Type of change


- [x] Performance Improvement

rag/nlp/query.py

                      ), tks
 
         def need_fine_grained_tokenize(tk):
-            if len(tk) < 4:
+            if len(tk) < 3:
                 return False
             if re.match(r"[0-9a-z\.\+#_\*-]+$", tk):
                 return False