Docs: Usage: use .lytex instead of .pdftex

The latter extension gives an error message saying that lilypond-book
does not understand the file extension.

diff --git a/Documentation/usage/lilypond-book.itely b/Documentation/usage/lilypond-book.itely
index 2abffff61eafd86ec168692d0a47bd6c8ddc0708..d184b1705ca33d209688b3bfe20588845f8a5f5e 100644 (file)
--- a/Documentation/usage/lilypond-book.itely
+++ b/Documentation/usage/lilypond-book.itely
@@ -793,7 +793,7 @@ Ghostscript package.
 To produce a PDF file through PDF@LaTeX{}, use
 
 @example
-lilypond-book --pdf yourfile.pdftex
+lilypond-book --pdf yourfile.lytex
 pdflatex yourfile.tex
 @end example