Remove vestigial assertions

Remove vestigial assertions

The inliner used to have its own import path, which required calling
special inline versions of the spill helpers; these asserts were intended
to ensure that these regular spill helpers are not invoked during inlining,
which they do by asserting against `fgGlobalMorph`, since that flag was set
during inlining in the old code.  The inliner has since been updated to
re-use the main import code, and also to run when `fgGlobalMorph` is not
set anyway.  So these helpers currently run successfully during inlining,
despite the stale comment; remove the bogus assertions.