fix: Add missing subsequent config details

[Joel-hanson]

This pull request updates the documentation for the Kafka Connect source connector for IBM MQ by readding the configuration option which got lost in one of the previous pull requests.

Documentation update:

• README.md: Added a new configuration option, mq.receive.subsequent.timeout.ms, which specifies the timeout (in milliseconds) for receiving messages from the queue manager on subsequent receives before returning to Kafka Connect. The default value is 0, and valid values are 1 or greater.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[thajinushehin]

LGTM