[matomo] Add `::float` to type casts in "Pages" model

[hellpe]

For some reason, only on newly imported Matomo data, Metabase sees some columns of the matomo.pages table (e.g. exit_nb_uniq_visitors) typed as "Text" and returns the following message when running the current "Pages" model:

ERROR: invalid input syntax for type integer: "5.0"

The issue can be fixed by adding ::float type casts to the coalesced SQL lines, as shown here: https://metabase.osp.cat/model/5281-pages/query