Steps to Repro:
1. Create a new or open attached project
2. Import any 3D FBX with animation from the asset store
3. Select FBX in Project window and go to the Animation tab in the Inspector window
4. Scroll down to the curves group and add a curve

Actual Result:
The old icon appears for removing curves

Expected Result:
New icons are used

Occurring with:
2019.3.0a8, 2019.3.0a3

Note: The new icons are introduced in 2019.3.0a3

Environment Used:
Windows 10 and Mac 10.14