travis: temporarily remove the coverage script
travis: temporarily remove the coverage script

It's currently failing with

.coverage.sh: line 26: bisect-report: command not found

Signed-off-by: David Scott <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@recoil.org>

samoht/ocaml-vchan,mirage/ocaml-vchan,mirage/ocaml-vchan,djs55/ocaml-vchan,djs55/ocaml-vchan,samoht/ocaml-vchan,djs55/ocaml-vchan,mirage/ocaml-vchan,samoht/ocaml-vchan