text/vnd.trolltech.linguist: require space or start tag closing > in magic

https://doc.qt.io/qt-5/linguist-ts-file-format.html

Avoids some more MPEG TS confusion. Hopefully that is -- I haven't
been able to locate MPEG TS samples that would be misdetected as
Linguist files in the first place. But because of that, I think it's
fair to assume that the sequence `<TS` is not that common in them, and
thus it followed by a space or the start tag closing `>` could
be even less common.

Not checking for `<TS/` as the root element may not be empty per the
DTD. Per [0] checking other whitespace besides the common space isn't
necessary either.

Refs #10

[0] !103 (comment 741219)
1 job for work/scop/linguist-xml-magic in 2 minutes and 12 seconds