docs(man): omit misleading mention of environment for -u NORC (#16379)

The phrase referred specifically to `$VIMINIT` and `$EXRC`, which
are parsed (and available with, e.g., `echo $VIMINIT` if set) but
of course not loaded since _any_ initialization is skipped. Hence
this is redundant and can be misleading.

man/nvim.1

@@ -177,8 +177,7 @@ If
 .Ar vimrc
 is
 .Cm NORC ,
-do not load any initialization files (except plugins),
-and do not attempt to parse environment variables.
+do not load any initialization files (except plugins).
 If
 .Ar vimrc
 is