On june 21, in https://github.com/freebsd/freebsd/commit/2a1f073196fc44d4f6252c425b353c1e571e5a80, pwm.9 is removed and instead a symlink is created between pwmbus.9 and pwm.9.
On july 10, in https://github.com/freebsd/freebsd/commit/11d2152585ded430a0ce88d8b52a9447b82d6e96 it's added to ObsoleteFiles.inc.
Attached patch removes it from ObsoleteFiles.inc, since the symlink seems very intentional.
Alternatively, the symlink should be removed instead.