Docs: Fix inconsistency in documents when using BashOperator with Jinja templating

[sjyangkevin]

Why

The BashOperator document has a warning about passing dag_run.conf directly into the bash_command. This usage is not suggested. However, in the Core Concepts - Dag Run document, the example use the pattern that is not recommended, which is an inconsistency. This PR fixes this by updating the example in the Core Concepts -Dag Run document.

BashOperator Document

Core Concepts - Dag Run Document

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