Fix specifying the charset when exporting as HTML
The QString::replace() had no effect because the stream actually
contains <!DOCTYPE html PUBLIC "-W3CDTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">, not just <!DOCTYPE html>.
Also, the <meta> tag should be inside the <head> section.
BUG: 374260
FIXED-IN: 17.08.0
Differential Revision: https://phabricator.kde.org/D7206