docs/config: Fix problem with HTML entities in template example

Since the default kind for soy template is html, certain characters in
the subject would be encoded as HTML and appear as e.g. "&" instead
of "&" in the link text. By using the "text" kind and the pre-escaped
subject the link title is as expected.

Change-Id: Ibe1eb6237af18d3d4b955fff9b68da4193240a93