Typo in texinfo.texi: Format of tag tables in info files

[Gavin Smith]

There appears to be a typo in the "Info Format Tag Table" node in the
texinfo manual:

--- doc/texinfo.texi.old        2014-03-21 18:51:48.000000000 +0000
+++ doc/texinfo.texi    2014-03-21 18:53:09.000000000 +0000
@@ -23812,8 +23812,8 @@ Here is an example:
 @example
 ^_
 Tag Table:
-Node: Top^_89
-Node: Ch1^_292
+Node: Top^?89
+Node: Ch1^?292
 ^_
 End Tag Table
 @end example