maint: fix bootstrap module lists for alignof

* bootstrap.conf (gnulib_modules): Remove alignof, which isn’t
needed since coreutils source modules don’t include alignof.h.
Add stdalign, since they depend on alignof working without
stdalign.h.

bootstrap.conf

@@ -27,7 +27,6 @@ gnulib_modules="
   $avoided_gnulib_modules
   acl
   alignalloc
-  alignof
   alloca
   announce-gen
   areadlink-with-size
@@ -248,6 +247,7 @@ gnulib_modules="
   stat-macros
   stat-size
   stat-time
+  stdalign
   stdbool
   stdlib-safer
   stpcpy