org.texi: minor fix: use english version for DATE.

Thanks to Giovanni Ridolfi for spotting this!

doc/org.texi

@@ -5,7 +5,7 @@
 @settitle The Org Manual
 
 @set VERSION 7.6
-@set DATE juillet 2011
+@set DATE July 2011
 
 @c Use proper quote and backtick for code sections in PDF output
 @c Cf. Texinfo manual 14.2