Remove atmospheric radius optimisation

[pgranger23]

In order to obtain some minimal gain on the atmospheric event generation time in reduced geometries (such as 1x2x6), the generation sphere radius was reduced from 70m down to 20m. Given that the efficiency gain is negligible (0.87 s/event vs 0.93 s/event) and that we are now moving to using full geometries, it is much cleaner to revert back to having a 70m radius as baseline.

[FNALbuild]

✔️ CI build for LArSoft Succeeded on slf7 for c14:prof -- details available through the CI dashboard

[FNALbuild]

✔️ CI build for LArSoft Succeeded on slf7 for e26:prof -- details available through the CI dashboard

[FNALbuild]

⚠️ CI build for DUNE Succeeded with warning at phase build on slf7 for c14:prof - ignored warnings for build -- details available through the CI dashboard

parent CI build details are available through the CI dashboard

[FNALbuild]

⚠️ CI build for DUNE Warning at phase ci_tests DUNE on slf7 for e26:prof - ignored warnings for build -- details available through the CI dashboard

🚨 For more details about the warning phase, check the ci_tests DUNE phase logs

parent CI build details are available through the CI dashboard

[leoaliaga]

@pgranger23, could you also assign one or two reviewers when you have a chance?