index.html: Use "Data Portal" for "Data" heading
index.html: Use "Data Portal" for "Data" heading

Now that we have all the other portals, we can be more specific.

Signed-off-by: Alan Orth <1ad53e5ac412470be257046982dc9c04920057fa@cgiar.org>

alanorth/data.ilri.org,alanorth/data.ilri.org