Rollup merge of #150968 - tgross35:remove-no-f16-f128, r=Amanieu

compiler-builtins: Remove the no-f16-f128 feature

This option was used to gate `f16` and `f128` when support across backends and targets was inconsistent. We now have the rustc builtin cfg `target_has_reliable{f16,f128}` which has taken over this usecase. Remove no-f16-f128 since it is now unused and redundant.