[meta.reflection.layout] change 'entity' to 'construct'

Fixes NB US 104-165 (C++26 CD).

Author: jwakely

source/meta.tex

@@ -5687,7 +5687,7 @@
 \pnum
 Let $V$ be the offset in bits from the beginning of a complete object
 of the type represented by \tcode{parent_of(r)}
-to the subobject associated with the entity represented by \tcode{r}.
+to the subobject associated with the construct represented by \tcode{r}.
 
 \pnum
 \returns