PYTHON-3019 Fix doc test failures (#794)

Remove pymongo 2 to 3 migration guide.
Make raw_bson doc tests less flakey.

Author: ShaneHarvey

bson/raw_bson.py

@@ -28,23 +28,23 @@
   >>> client.drop_database('db')
   >>> client.drop_database('replica_db')
   >>> db = client.db
-  >>> result = db.test.insert_many([{'a': 1},
-  ...                               {'b': 1},
-  ...                               {'c': 1},
-  ...                               {'d': 1}])
+  >>> result = db.test.insert_many([{'_id': 1, 'a': 1},
+  ...                               {'_id': 2, 'b': 1},
+  ...                               {'_id': 3, 'c': 1},
+  ...                               {'_id': 4, 'd': 1}])
   >>> replica_db = client.replica_db
   >>> for doc in db.test.find():
   ...    print(f"raw document: {doc.raw}")
   ...    print(f"decoded document: {bson.decode(doc.raw)}")
   ...    result = replica_db.test.insert_one(doc)
   raw document: b'...'
-  decoded document: {'_id': ObjectId('...'), 'a': 1}
+  decoded document: {'_id': 1, 'a': 1}
   raw document: b'...'
-  decoded document: {'_id': ObjectId('...'), 'b': 1}
+  decoded document: {'_id': 2, 'b': 1}
   raw document: b'...'
-  decoded document: {'_id': ObjectId('...'), 'c': 1}
+  decoded document: {'_id': 3, 'c': 1}
   raw document: b'...'
-  decoded document: {'_id': ObjectId('...'), 'd': 1}
+  decoded document: {'_id': 4, 'd': 1}
 
 For use cases like moving documents across different databases or writing binary
 blobs to disk, using raw BSON documents provides better speed and avoids the

doc/changelog.rst

@@ -1881,7 +1881,9 @@ Changes in Version 2.9
 Version 2.9 provides an upgrade path to PyMongo 3.x. Most of the API changes
 from PyMongo 3.0 have been backported in a backward compatible way, allowing
 applications to be written against PyMongo >= 2.9, rather then PyMongo 2.x or
-PyMongo 3.x. See the :doc:`/migrate-to-pymongo3` for detailed examples.
+PyMongo 3.x. See the `PyMongo 3 Migration Guide
+<https://pymongo.readthedocs.io/en/3.12.1/migrate-to-pymongo3.html>`_ for
+detailed examples.
 
 .. note:: There are a number of new deprecations in this release for features
   that were removed in PyMongo 3.0.

doc/index.rst

@@ -34,9 +34,6 @@ everything you need to know to use **PyMongo**.
 :doc:`migrate-to-pymongo4`
   A PyMongo 3.x to 4.x migration guide.
 
-:doc:`migrate-to-pymongo3`
-  A PyMongo 2.x to 3.x migration guide.
-
 :doc:`python3`
   Frequently asked questions about python 3 support.
 
@@ -123,5 +120,4 @@ Indices and tables
    changelog
    python3
    migrate-to-pymongo4
-   migrate-to-pymongo3
    developer/index