docs(openlineage): fix quotation around openlineage transport value

[timonviola]

The docs suggests that the transport option should be quoted using ' in airflow.cfg. Using the described configuration results in {{utils.py:408}} WARNING - Unable to parse [openlineage] 'transport' as valid json message. Removing the quotation marks around the transport config entry fixes this.

The generated airflow.cfg shows the correct version of the config:

# Pass OpenLineage Client transport configuration as JSON string. It should contain type of the 
# transport and additional options (different for each transport type). For more details see:   
# https://openlineage.io/docs/client/python/#built-in-transport-types                           
#                                                                                               
# Currently supported types are:                                                                
#                                                                                               
#   * HTTP                                                                                      
#   * Kafka                                                                                     
#   * Console                                                                                   
#   * File                                                                                      
#                                                                                               
# Example: transport = {"type": "http", "url": "http://localhost:5000", "endpoint": "api/v1/lineage"}

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