[lldb][NFC] Remove unused custom reimplementation of realpath for Windows
No one is calling this function it seems and according to
https://bugs.llvm.org/show_bug.cgi?id=47088 this can leak memory, so let's just
Quote from the bug report:
Before return on line 146, the memory allocated on line 130 is not freed.
Reviewed By: amccarth
Differential Revision: https://reviews.llvm.org/D85633