SmallVectorTest: Remove some more robust checks added in r210429 since they caught some bugs I haven't fixed yet.

Specifically this caused inserting an element from a SmallVector into
itself when such an insertion would cause a reallocation. We have code
to handle this for non-reallocating cases, but it's not robust against
reallocation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210430 91177308-0d34-0410-b5e6-96231b3b80d8