docs: improve Release Cadence section formatting

[a-ariff]

Added colon and space after "Release Cadence" for better readability and consistent section header formatting in the Get involved section.

This is a minor documentation formatting improvement that makes the Release Cadence section header clearer by adding proper punctuation.

Documentation Changes

• Improved formatting consistency in README.md

[propel-code-bot]

This pull request makes minor formatting improvements to the README.md file. A colon and space have been added after the 'Release Cadence' subsection in the 'Get involved' section to enhance readability and maintain consistent formatting with other section headers.

This summary was automatically generated by @propel-code-bot

[github-actions]

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Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
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Quality

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[propel-code-bot]

[Documentation]

Capitalize 'pypi' to 'PyPI' for correct proper-noun formatting.