Exclude `project.yml` as rev-depgraph node key
Exclude `project.yml` as rev-depgraph node key

This commit changes the debug log output.

Nothing ever depends on `project.yml`, so don't include it as a node key
in reverse dependency graphs.  This change removes some zero-information
lines from the debug output.

apache/incubator-mynewt-newt,apache/incubator-mynewt-newt