Fix CONTRIBUTORS_QUICK_START Doc

[namsick96]

• According to Development Environment Setting Guide in CONTRIBUTORS_QUICK_START.rst Airflow Backend DB is PostgreSQL (activated by breeze)
• But DB Connection Setting Guide was based on MySQL DB.
• Thus, Changing MySQL DB Connection Guide to PostgreSQL Guide and replace images that inform db management tool connection.

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^ Add meaningful description above

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In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
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[namsick96]

@uranusjr Thanks for Spelling check and formatting!
Is there anything i should do for merge this commit to main branch?

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[uranusjr]

Needed to wait for CI to pass.