[depr.conversions.string] Use proper "Returns:" markup. (#4120)

Eelis · tkoeppe · commit 3e7dce381f76 · 2020-09-24T01:26:49.000+01:00
diff --git a/source/future.tex b/source/future.tex
@@ -2316,7 +2316,8 @@
 
 \begin{itemdescr}
 \pnum
-returns \tcode{cvtstate}.
+\returns
+\tcode{cvtstate}.
 \end{itemdescr}
 
 \indexlibrarymember{state_type}{wstring_convert}%
