[whatwg] typo in UTF-16LE BOM sniffing rule

[Dan Winship]

In the summary table at the end of "2.7.4 Content-Type sniffing: unknown
type", the UTF-16LE BOM is incorrectly listed as "FF FF" instead of "FF
FE". (The UTF-16BE BOM is correct, and the UTF-16LE one is stated
correctly earlier in the text):

FF FF 00 00 	FE FF 00 00 	text/plain 	n/a 	UTF-16BE BOM
FF FF 00 00 	FF FF 00 00 	text/plain 	n/a 	UTF-16LE BOM
                   ^^
FF FF FF 00 	EF BB BF 00 	text/plain 	n/a 	UTF-8 BOM

-- Dan