Delete the removeCallEdgeTo callgraph method,

Delete the removeCallEdgeTo callgraph method,
because it does not maintain a correct list
of callsites.  I discovered (see following
commit) that the inliner will create a wrong
callgraph if it is fed a callgraph with
correct edges but incorrect callsites.  These
were created by Prune-EH, and while it wasn't
done via removeCallEdgeTo, it could have been
done via removeCallEdgeTo, which is an accident
waiting to happen.  Use removeCallEdgeFor
instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55859 91177308-0d34-0410-b5e6-96231b3b80d8