Switching between a duplicate sprite and original sprite triggers project changed state

[kchadha]

Expected Behavior

Switching sprites should not cause "Save Now" to appear in menu bar.

Actual Behavior

Switching between two sprites (A and B) where A has blocks and B is a duplicate of A, triggers a project changed state and should not. This is related to scratchfoundation/scratch-gui#4573

Steps to Reproduce

1. Create a new project
2. Add blocks to Sprite1
3. Duplicate Sprite1
4. Click "Save Now"
5. Switch back to Sprite1, notice that "Save Now" appears