[meta.reflection.layout] Delete unintended "value".

This seems to have been copy-pasted erroneously.

Author: tkoeppe

source/meta.tex

@@ -5783,7 +5783,6 @@
 \tcode{dealias(r)} is a reflection of a
 type,
 object,
-value,
 variable of non-reference type,
 non-static data member that is not a bit-field,
 direct base class relationship, or