Fix overlap damage calculation for both Explosive Trap and Explosive Trap of Shrapnel
Fixes #7260.
Steps taken to verify a working solution:
-Checked pob.
Link to a build that showcases this PR:
https://pobb.in/lZ0fQfewRtIY
Before screenshot:
After screenshot:
It looks like You tried to fix it by making it in line with the tooltip, but in this case the tooltip was incorrect, since this was mostly copied over from seismic trap (that's why it's referring to 'waves').
The overlap calculation for explosive trap is supposed to be (tertiary radius + enemy radius - 1) ^ 2 / secondary radius ^ 2.
So in the code the tertiary radius was correct, but it should have been the secondary radius in place of where the primary radius was. Before this just so happened to work because the regular explosive trap has equal primary and secondary radii.
Superceded by #7384