I don't see anything depending on it in the RPM specs file archive.
It looks like the configure script might get confused when building with
future C compilers which do not accept implicit function declarations,
and it's probably not worth porting this to C99.
According to my repoquery, erlang-js still uses mozjs68:
$ dnf repoquery --whatrequires mozjs68 --disablerepo='*' --enablerepo=rawhide
Fedora - Rawhide - Developmental packages for the next Fedora release 36 kB/s | 10 kB 00:00
Fedora - Rawhide - Developmental packages for the next Fedora release 23 MB/s | 64 MB 00:02
Last metadata expiration check: 0:00:13 ago on Tue 29 Nov 2022 11:18:22 AM CET.
When it is time to retire mozjs68 (apparently not yet because of erlang-js, but hopefully soon :) ), please add mozjs68 to fedora-obsolete-packages because a lot of users probably still have it installed and it is going to get broken deps and break the update path as soon as icu gets updated in rawhide.