Address doctest failure

Signed-off-by: Margarit Hakobyan <[email protected]>

Author: margarit-h

docs/user/dql/functions.rst

@@ -2347,7 +2347,7 @@ Return type integer:
 
 Example::
 
-    os> SELECT POSITION('world' IN 'helloworld')
+    opensearchsql> SELECT POSITION('world' IN 'helloworld'), POSITION('invalid' IN 'helloworld');
     fetched rows / total rows = 1/1
     +-------------------------------------+---------------------------------------+
     | POSITION('world' IN 'helloworld')   | POSITION('invalid' IN 'helloworld')   |