Fix rendering with mandoc(1).

Index: doc/gsl.3
--- doc/gsl.3.orig
+++ doc/gsl.3
@@ -11,9 +11,8 @@ team in C, and present a modern Applications Programmi
 level languages.
 .PP
 The library covers the following areas,
-.TP
+.PP
 .nf
-.BR
 Complex Numbers
 Roots of Polynomials
 Special Functions