bug#31217: 12.1.1; typo in TeX-expand-list's "docstring"

[jfbu]

Remember to cover the basics.  Including a minimal LaTeX example
file exhibiting the problem might help.

When doing C-h v TeX-expand-list the following pops up

----
TeX-expand-list is a compiled Lisp function in ‘tex.el’.

(TeX-expand-list)

Complete list of expansion strings for TeX command names.

Concatenate ‘TeX-expand-list’ and ‘TeX-expand-list-bultin’ making
sure "%p" is the first entry.
----

there is a typo s/bultin/builtin

Emacs  : GNU Emacs 25.2.3 (x86_64-apple-darwin13.4.0, Carbon Version 157 AppKit 
1265.21)
 of 2017-08-26
Package: 12.1.1