Fix -Wdeprecated warnings due to the use of copy ops on SCEVPredicate derived class objects

SCEVUnionPredicate is copied constructed here: lib/Transforms/Scalar/LoopDistribute.cpp:793
and move assigned (which can use the base class's copy ctor just
fine/without extra cost (I'd add it if it weren't for MSVC's issues
meaning = default is insufficient)) here: lib/Transforms/Utils/LoopVersioning.cpp:46

llvm-svn: 252537