[test][lldb-vscode] Un-realpath coreFile test.

[test][lldb-vscode] Un-realpath coreFile test.

TestVSCode_coreFile looks for an exe/core file in the same directory as the test. It first calls `realpath`, but I don't think it's necessary. Using `realpath` prevents this test from working when run as part of a build system that uses content-addressed-storage, i.e. all the files might all be symlinks in the same directory pointing to files in different directories elsewhere. If some amount of normalization is needed, maybe `os.path.normpath()` would be useful, although I wouldn't see why that's needed either.

(This is a fairly trivial patch, but I'm mailing it to see if there is a reason we need to keep `realpath`, and if so, if there's some other workaround we can do).

Differential Revision: https://reviews.llvm.org/D138345