Updates coverage model submodule

Previous HEAD position was c339b71... Merge pull request #113 from
lukecampbell/timeseries-r2
HEAD is now at 90dfd08... Merge pull request #120 from
ooici/submodules-r2
Merge pull request #1369 from lukecampbell/cov-update-r2

OOIION-1310 Updates Coverage Model Reference