Change experimental_python_types to legacy_primitive_types. Invert lo…

…gic behind interpreting this parameter.

README.md

@@ -116,7 +116,7 @@ engine = create_engine(
     connect_args={
       "session_properties": {'query_max_run_time': '1d'},
       "client_tags": ["tag1", "tag2"],
-      "experimental_python_types": True,
+      "legacy_primitive_types": True,
       "roles": {"catalog1": "role1"},
     }
 )
@@ -126,7 +126,7 @@ engine = create_engine(
     'trino://user@localhost:8080/system?'
     'session_properties={"query_max_run_time": "1d"}'
     '&client_tags=["tag1", "tag2"]'
-    '&experimental_python_types=true'
+    '&legacy_primitive_types=true'
     '&roles={"catalog1": "role1"}'
 )
 
@@ -135,7 +135,7 @@ engine = create_engine(URL(
   host="localhost",
   port=8080,
   client_tags=["tag1", "tag2"],
-  experimental_python_types=True
+  legacy_primitive_types=True
 ))
 ```
 
@@ -442,8 +442,9 @@ exits the *with* context and the queries succeed, otherwise
 
 ## Improved Python types
 
-If you enable the flag `experimental_python_types`, the client will convert the results of the query to the 
+By default, the client will convert the results of the query to the
 corresponding Python types. For example, if the query returns a `DECIMAL` column, the result will be a `Decimal` object.
+If you want to disable this behaviour, set flag `legacy_primitive_types` to `True`.
 
 Limitations of the Python types are described in the 
 [Python types documentation](https://docs.python.org/3/library/datatypes.html). These limitations will generate an 
@@ -456,7 +457,6 @@ import pytz
 from datetime import datetime
 
 conn = trino.dbapi.connect(
-    experimental_python_types=True,
     ...
 )