Remove add_to_queue and remove_from_queue from LightningModule

[shenoynikhil]

What does this PR do?

Part of #12521

resolves #9118

Does your PR introduce any breaking changes? If yes, please list them.

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[shenoynikhil]

@akihironitta Can you have a look at this? Also sorry for the delay.

[akihironitta]

@akihironitta Can you have a look at this? Also sorry for the delay.

No worries! I'm sorry if I rushed you in any way. I just wanted to make sure that breaking changes like this wouldn't be made at the very last minute before the next 1.7 release :)

Thank you again for your contribution, @shenoynikhil!