Fix pool docstring.

Author: behackett

pymongo/pool.py

@@ -301,7 +301,7 @@ def command(self, dbname, spec, slave_ok=False,
  - `read_concern`: The read concern for this command.
  - `write_concern`: The write concern for this command.
  - `parse_write_concern_error`: Whether to parse the
- ``writeConcernError` field in the command response.
+ ``writeConcernError`` field in the command response.
  """
  if self.max_wire_version < 4 and not read_concern.ok_for_legacy:
  raise ConfigurationError(