FIXUP LWG3847: Add blank line before \pnum.

Author: burblebee

source/ranges.tex

@@ -2405,6 +2405,7 @@
 \mandates
 For the first overload,
 \tcode{C} is a cv-unqualified class type.
+
 \pnum
 \returns
 A range adaptor closure object\iref{range.adaptor.object} \tcode{f}