[llvm-cov] Do not print out the filename of the object file

[llvm-cov] Do not print out the filename of the object file

When we load coverage data from multiple objects, we don't have a way to
attribute a source object to a function record. Printing out the object
filename next to the source filename is already not very useful: soon,
it'll actually become misleading. Stop printing out the filename now.

llvm-svn: 285043