Remove mesh triangles in contour plot

How do I get rid of the mesh in this contour plot?

 ContourPlot[x^2 + y^2, {x, -10, 10}, {y, -10, 10},      Contours -> {1.0, 4.0, 10.5}, ContourStyle -> None,      ContourShading -> {RGBColor[1, .2, 0, .1], RGBColor[1, .2, 0, .3],      RGBColor[1, .2, 0, .5], RGBColor[1, .2, 0, .7]}] 

enter image description here

Setting the option Mesh->None doesn’t help. I’m using Mathematica 12.1.1