Fix additional < followed by characters and EOF issues (#728)

[willkg]

This fixes these two cases:

• "<some thing thing" where "thing" is repeated twice which kicks up a parser error because it thinks it's a duplicated attribute
• "<some thing thing2 " where the space at the end causes a expected-end-of-tag-but-got-eof parser error to pop up

In both of these cases, we want the data to be treated as character data--not a tag.

Python 3.10.14 (main, Aug 14 2024, 05:11:29) [Clang 18.1.8 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import bleach
>>> bleach.clean("<test abc abc")
'&lt;test abc abc'
>>> bleach.clean("<test abc ")
'&lt;test abc '
>>> bleach.clean("asd<test abc ")
'asd&lt;test abc '
>>>

Fixes #728.

[willkg]

self-r+