[Orc][MCJIT] Remove the small code model regression tests.

These regression tests are supposed to test small code model support, but have
been XFAIL'd because we don't have an in-tree memory manager that can guarantee
a small-code-model compatible memory layout. Unfortunately, they can
occasionally pass if they get lucky with memory allocation, causing unexpected
passes on the bots. That's not very helpful.

I'm going to remove these until we have the infrastructure (small-code-model
compatible memory manager) to run them properly.

llvm-svn: 233722