[whatwg] Typos in spec

[Aryeh Gregor]

In 2.1.2:

"A content attribute is said to change value only if its value new
value is different than its previous value; setting an attribute to a
value it already has does not change it."

should be

"A content attribute is said to change value only if its new value is
different than its previous value; setting an attribute to a value it
already has does not change it."

In 2.1.5:

"This includes such encodings as Shift_JIS and variants of ISO-2022,
even though it is possible in this encodings for bytes like 0x70 to be
part of longer sequences that are unrelated to their interpretation as
ASCII."

should be

"This includes such encodings as Shift_JIS and variants of ISO-2022,
even though it is possible in these encodings for bytes like 0x70 to
be part of longer sequences that are unrelated to their interpretation
as ASCII."