Use Cairo 2.15.0 to checkout tests

[gabrielbosio]

Depends on #1494

Change the cairo-tests make command (Link) so that it uses the tests from Cairo 2.15.0 instead of Cairo 2.14.0.

[JulianGCalderon]

We should be able to use CAIRO_2_VERSION Makefile variable, to automate the process of updating the tests.