[2D][Sprite Atlas] Sprite Atlas assets are unable to upgrade.

On changing Sprite packer mode from "Sprite Atlas V2 (Experimental)" to "Sprite Atlas V1-Always Enabled " Sprite Atlas assets are unable to upgrade its file type in breadcrumb bar in the project window.

Repro steps:
1. Create a New Project with 2D template.
2. In Editor Settings, set sprite packer mode to "Sprite Atlas V2 (Experimental)"
3. Create new sprite atlas.
4. In Project window observe the name of sprite atlas asset in the breadcrumb bar(.spriteatlasv2)
5. In Editor Settings, set sprite packer mode to "Sprite Atlas V1-Always Enabled "
6. Observe the existing sprite atlas do not upgrade to .spriteatlas

Expected result: Sprite Atlas should upgrade and use .spriteatlas file type
Actual result: Sprite Atlas still have .spriteAtlasv2 file type

Reproducible on:
2020.2.0a19, 2020.1.0f1
Note: Sprite Atlas V2 packer mode is implemented in 2020.1.0a1

Environment:
Windows 10 and Mac 10.15