[LLDB][Test] Remove `skipIfWindows` for conditional breakpoint test (NFC)

Summary:
The test for conditional breakpoints on Windows was skipped because
there was no expression evaluation support at the time it was written.

After removing the annotation and testing it again, the test is passing.
http://lists.llvm.org/pipermail/lldb-dev/2019-August/015405.html



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

Reviewers: stella.stamenova, jingham

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D66499

llvm-svn: 369453