Partially revert ac76bc1145dd because it is no longer necessary

In ac76bc1145dd, I added a few volatiles to work around ctrig_test
failures with {inf,inf}. This is not necessary anymore now, since in
3b00222f156d we added -fp-exception-behavior=maytrap for clang >= 10 in
libm's Makefile. (The flag tells clang to use stricter floating point
semantics, which libm depends on.)

PR: 244732, 254911
Fixes: ac76bc1145dd

(cherry picked from commit e2157cd0000f6dbb6465d7a885f2dcfd4d3596cb)