MNT: Explicitly point CodeCov to our coverage.xml
MNT: Explicitly point CodeCov to our coverage.xml

This way we only generate the XML once and avoid it detecting any
spurious files.

ahaberlie/MetPy,ShawnMurd/MetPy,Unidata/MetPy,dopplershift/MetPy,dopplershift/MetPy,ahaberlie/MetPy,Unidata/MetPy