Alpha Channel Created when 'Accumulator Includes Alpha' is Disabled in MRQ

Occurs 3/3 times

Alpha Channel Created when 'Accumulator Includes Alpha' is Disabled in MRQ issue discovered in LiveQA, and appears related to FORT-451157

Note: Whether 'Accumulator Includes Alpha' is enabled or disabled in the MRQ Render settings an opaque alpha channel is generated. 

Repro Steps:

1. Opened a blank project and enabled MRQ.
2. In the project settings, enabled alpha support by selecting 'Allow Through ToneMapper'.
3. Added a cube to the level.
4. Added a level sequencer with a Camera focused on the cube.
5. Set camera transform to dolly in on the Cube and add keyframes for transform.
6. Set the Render Queue settings to include .png and in Deferred Rendering leave 'Accumulator Includes Alpha' unchecked.
7. Set the Output to render 0-60 frames.
8. Saved the level sequencer and level.
9. Rendered local.

Expected: .pngs should not include alpha channel with 'Accumulate Includes Alpha' unchecked.
Actual: Rendered .pngs do include an alpha channel.

Alpha Channel not working in MRQ UE5