doc: fix incorrect section title

Reported by Gaurav Singh <gaurav.singh199709@yahoo.com>.
https://lists.gnu.org/r/bug-bison/2020-11/msg00000.html

* doc/bison.texi (Rpcalc Expr): Rename as...
(Rpcalc Exp): this, as the nterm is named 'exp'.

1 files changed, 4 insertions, 4 deletions

diff --git a/doc/bison.texi b/doc/bison.texi
index 277aba29..416a8ec6 100644
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -303,7 +303,7 @@ Grammar Rules for @code{rpcalc}
 
 * Rpcalc Input::            Explanation of the @code{input} nonterminal
 * Rpcalc Line::             Explanation of the @code{line} nonterminal
-* Rpcalc Expr::             Explanation of the @code{expr} nonterminal
+* Rpcalc Exp::              Explanation of the @code{exp} nonterminal
 
 Location Tracking Calculator: @code{ltcalc}
 
@@ -1788,7 +1788,7 @@ rule are referred to as @code{$1}, @code{$2}, and so on.
 @menu
 * Rpcalc Input::            Explanation of the @code{input} nonterminal
 * Rpcalc Line::             Explanation of the @code{line} nonterminal
-* Rpcalc Expr::             Explanation of the @code{expr} nonterminal
+* Rpcalc Exp::              Explanation of the @code{exp} nonterminal
 @end menu
 
 @node Rpcalc Input
@@ -1853,8 +1853,8 @@ uninitialized (its value will be unpredictable).  This would be a bug if
 that value were ever used, but we don't use it: once rpcalc has printed the
 value of the user's input line, that value is no longer needed.
 
-@node Rpcalc Expr
-@subsubsection Explanation of @code{expr}
+@node Rpcalc Exp
+@subsubsection Explanation of @code{exp}
 
 The @code{exp} grouping has several rules, one for each kind of expression.
 The first rule handles the simplest expressions: those that are just