docs: update libpeas-sections.txt
docs: update libpeas-sections.txt

It was missing the new peas_extension_set_foreach and had some old
functions.

Bug #653703

chergert/libpeas,Distrotech/libpeas,GNOME/libpeas,GNOME/libpeas,gregier/libpeas,chergert/libpeas,chergert/libpeas,gregier/libpeas,Distrotech/libpeas,Distrotech/libpeas,gregier/libpeas,gregier/libpeas