chore: pin rds package version in databuilder

[xuan616]

Summary of Changes

• Pin rds package version to 0.0.5 in databuilder to make it consistent with metadata_service
• Bump databuilder version to 6.2.1
• Removed the stale 'ToDo' comment in sample_data_loader_mysql.py

Tests

No real code change

N/A

Documentation

N/A

CheckList

Make sure you have checked all steps below to ensure a timely review.

• PR title addresses the issue accurately and concisely. Example: "Updates the version of Flask to v1.0.2"
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.
• PR includes a summary of changes.
• PR adds unit tests, updates existing unit tests, OR documents why no test additions or modifications are needed.
• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does