[stringbuf.cons] Insert missing space after comma (#4335)

CaseyCarter · web-flow · commit 6c12819b6a5b · 2020-11-10T22:22:05.000Z
This is the common library style.
diff --git a/source/iostreams.tex b/source/iostreams.tex
@@ -7726,7 +7726,7 @@
 \begin{itemdescr}
 \pnum
 \constraints
-\tcode{is_same_v<SAlloc,Allocator>} is \tcode{false}.
+\tcode{is_same_v<SAlloc, Allocator>} is \tcode{false}.
 
 \pnum
 \effects
