Fix failing mapReduce doctests caused by the MR in Agg project

Document: examples/aggregation

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File "examples/aggregation.rst", line 121, in default

Failed example:

    for doc in result.find():

      pprint.pprint(doc)

Expected:

    {'_id': 'cat', 'value': 3.0}

    {'_id': 'dog', 'value': 2.0}

    {'_id': 'mouse', 'value': 1.0}

Got:

    {'_id': 'cat', 'value': 3.0}

    {'_id': 'mouse', 'value': 1.0}

    {'_id': 'dog', 'value': 2.0}

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File "examples/aggregation.rst", line 139, in default

Failed example:

    pprint.pprint(

        db.things.map_reduce(mapper, reducer, "myresults", full_response=True))

Expected:

    {...'counts': {'emit': 6, 'input': 4, 'output': 3, 'reduce': 2},

     'ok': ...,

     'result': '...',

     'timeMillis': ...}

Got:

    {'$clusterTime': {'clusterTime': Timestamp(1581123789, 1669),

                      'signature': {'hash': '\x00\x00\x00\x00\x00\x00\x00\x00'

                                            '\x00\x00\x00\x00\x00\x00\x00\x00'

                                            '\x00\x00\x00\x00',

                                    'keyId': 0}},

     'ok': 1.0,

     'operationTime': Timestamp(1581123789, 1669),

     'result': 'myresults'}

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File "examples/aggregation.rst", line 154, in default

Failed example:

    for doc in results.find():

      pprint.pprint(doc)

Expected:

    {'_id': 'cat', 'value': 1.0}

    {'_id': 'dog', 'value': 1.0}

Got:

    {'_id': 'dog', 'value': 1.0}

    {'_id': 'cat', 'value': 1.0}

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File "examples/aggregation.rst", line 166, in default

Failed example:

    pprint.pprint(

        db.things.map_reduce(

            mapper,

            reducer,

            out=SON([("replace", "results"), ("db", "outdb")]),

            full_response=True))

Expected:

    {...'counts': {'emit': 6, 'input': 4, 'output': 3, 'reduce': 2},

     'ok': ...,

     'result': {'collection': ..., 'db': ...},

     'timeMillis': ...}

Got:

    {'$clusterTime': {'clusterTime': Timestamp(1581123789, 1678),

                      'signature': {'hash': '\x00\x00\x00\x00\x00\x00\x00\x00'

                                            '\x00\x00\x00\x00\x00\x00\x00\x00'

                                            '\x00\x00\x00\x00',

                                    'keyId': 0}},

     'ok': 1.0,

     'operationTime': Timestamp(1581123789, 1678),

     'result': {'collection': 'results', 'db': 'outdb'}}

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1 items had failures: