Chart: Allow disabling git-sync for Webserver

[kaxil]

closes #11704

When DAG Serialization is enabled for Airflow >= 1.10.10, <2.0, we don't need to run git-sync container for Webserver as DAGs are fetched from Database. DAG Serialization is enabled for Airflow > 2 so users should be able to stop running §git-sync` containers for Webserver when by running:

helm upgrade airflow . \
  --set dags.gitSync.enabled=true \
  --set dags.gitSync.excludeWebserver=true

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[mik-laj]

For Airflow 1.10.9 and earlier, DAG files is still needed for DAG code ttab. For Airflow 1.10.10 and newer (including 2.0.0), it is needed to enablestore_dag_code to True (default value: False). DAG Serialization is not enough.
http://airflow.apache.org/docs/apache-airflow/2.0.1/configurations-ref.html#store-dag-code

[kaxil]

We had removed the default and have a fallback of True for store_dag_code for Airflow >=1.10.11

airflow/airflow/settings.py

Lines 460 to 462 in 5da8319

	# Whether to persist DAG files code in DB. If set to True, Webserver reads file contents
	# from DB instead of trying to access files in a DAG folder.
	STORE_DAG_CODE = conf.getboolean("core", "store_dag_code", fallback=True)

airflow/airflow/config_templates/default_airflow.cfg

Lines 205 to 209 in 5da8319

	# Whether to persist DAG files code in DB.
	# If set to True, Webserver reads file contents from DB instead of
	# trying to access files in a DAG folder.
	# Example: store_dag_code = False
	# store_dag_code =

Same for 1.10.11:

https://github.com/apache/airflow/blob/1.10.11/airflow/config_templates/default_airflow.cfg#L237-L242

where the value is same as store_serialized_dags:

https://github.com/apache/airflow/blob/1.10.11/airflow/settings.py#L431-L434

[kaxil]

I updated the description in fb10b09

[github-actions]

The Workflow run is cancelling this PR. Building images for the PR has failed. Follow the workflow link to check the reason.

[github-actions]

The Workflow run is cancelling this PR. Building images for the PR has failed. Follow the workflow link to check the reason.

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest master at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[ashb]

Could you update this PR title and description please?