Remove bogus #include added by
d4e71df6d75.
The recently added inclusion of guc.h in smgr.h is not necessary and
introduces more server-related stuff. Removing the directive helps
avoid potential issues with including sgmr.h in frontends.
Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/
20230425.115748.
2130383825066921512.horikyota.ntt%40gmail.com