doc: improve yacc man page fonts
Problem reported by Helge Kreutzmann in:
https://lists.gnu.org/r/bug-bison/2025-12/msg00000.html
* doc/yacc.1.in: Fix fonts.
diff --git a/doc/yacc.1.in b/doc/yacc.1.in
index 1d07483..e85bbff 100644
--- a/doc/yacc.1.in
+++ b/doc/yacc.1.in
@@ -5,14 +5,15 @@
.B yacc
[\fIOPTION\fR]... \fIFILE\fR
.SH DESCRIPTION
-.I Yacc
+The program
+.B yacc
(Yet Another Compiler Compiler) is a parser generator. This
version is a simple wrapper around
-.IR bison (1).
+.BR bison (1).
It passes option
\fB\-y\fR, \fB\-\-yacc\fR
to activate the upward compatibility mode. See
-.IR bison (1)
+.BR bison (1)
for more information.
.SH AUTHOR
Written by Paul Eggert.
