[IMP] oca-gen-addon-readme: stop emitting an XML declaration

[nilshamerlinck]

#595

[pedrobaeza]

But this should be only for 17.0, not the rest of the versions.

[bosd]

LGTM, dunno if it is a blocker to do this for all versions

[nilshamerlinck]

Hello guys :)

• thanks for looking into this PR!
• it's ok to apply this change for all versions: it will not change anything even for old odoo instances that would not have been patched with the fixes [FIX] base: correctly parse utf8 html module descriptions odoo/odoo#133708 and [FIX] base: encoding guessing of html module descriptions odoo/odoo#133900
• that's because we never actually strictly needed the XML declaration, because docutils also adds this meta tag in the index.html: <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> that is respected by the HTMLParser used by lxml.html.document_fromstring(doc)
• I updated the commit to make this a bit more explicit

[sbidoul]

Thanks!