Remove AccleratorConnector.device_type

[DuYicong515]

What does this PR do?

Fixes #12077 (motivation and alternatives can be found in the issue)
Part of #11449: deprecate unused properties in accelerator_connector

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

None

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cc @four4fish

[krshrimali]

Just a minor suggestion, if there is an alternate for the user to know the device type now, will be good to add in the issue/PR description. Shouldn't block merging this PR. LGTM!

[DuYicong515]

Just a minor suggestion, if there is an alternate for the user to know the device type now, will be good to add in the issue/PR description. Shouldn't block merging this PR. LGTM!

That's a great suggestion! @krshrimali I'll add more contexts and info onto the issue and PR.

[krshrimali]

Awesome, thank you so much for considering the suggestion! 💯 @DuYicong515