heatmaps don't work with PolarAxis in GLMakie

[ffreyer]

• what version of Makie are you running? 0.21.7 master
• can you reproduce the bug with a fresh environment ? yes
• What platform + GPU are you on? irrelevant

This doesn't show any plot for me in GLMakie, but does in CairoMakie and WGLMakie:

fig = Figure()
ax = PolarAxis(fig[1, 1])
heatmap!(ax, rand(10, 10))
fig

Possibly caused by #4125 not catching the transform func from PolarAxis as a reason to not use image