-Wpass-failed warns when an explicitly requested optimization
(e.g. `#pragma GCC unroll`) cannot be performed. Since the standard
library contains those pragmas, this is more or less out of a
developer's control. We can play with inlining, but cannot guarantee
it will work.
Since the condition isn't fatal in any way, degrade it back to its
default disposition, a warning (it was upgraded to an error via
-Werror). Don't suppress it entirely since in hot paths we do want
to address it.
Closesscylladb/scylladb#29980