Fixup

LWG noticed that these conditions were missing 'is true' so I offered to
editorially change them to math expressions.

Author: jwakely

source/memory.tex

@@ -3952,11 +3952,11 @@
 \begin{itemdescr}
 \pnum
 \expects
-\tcode{get() != nullptr}.
+\tcode{get() != nullptr} is \tcode{true}.
 
 \pnum
 \hardexpects
-\tcode{i <= 0}. If \tcode{T} is \tcode{U[N]}, \tcode{i < N}.
+$\tcode{i} \ge 0$. If \tcode{T} is \tcode{U[N]}, $\tcode{i} < \tcode{N}$.
 
 \pnum
 \returns