[analyzer] Remove obsolete ObjCPropRef SVal kind.

ObjC properties are handled through their semantic form of ObjCMessageExprs
and their wrapper PseudoObjectExprs, and have been for quite a while. The
syntactic ObjCPropertyRefExprs do not appear in the CFG and are not visited
by ExprEngine.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160458 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed