docs: prevent warnings due to autosectionlabel

Changeset 58ad30cf ("docs: fix reference to core-api/namespaces.rst")
enabled a new feature at Sphinx: it will now generate index for each
document title, plus to each chapter inside it.

There's a drawback, though: one document cannot have two sections
with the same name anymore.

A followup patch will change the logic of autosectionlabel to
avoid most creating references for every single section title,
but still we need to be able to reference the chapters inside
a document.

There are a few places where there are two chapters with the
same name. This patch renames one of the chapters, in order to
avoid symbol conflict within the same document.

PS.: as I don't speach Chinese, I had some help from a friend
(Wen Liu) at the Chinese translation for "publishing patches"
for this document:

	Documentation/translations/zh_CN/process/5.Posting.rst

Fixes: 58ad30cf ("docs: fix reference to core-api/namespaces.rst")
Signed-off-by: Mauro Carvalho Chehab <mch...