[lldb] Disable `watchpoint_callback.test` temporarily on darwin

This test started failing on the green-dragon bot, but after some
investigation, it doesn't have anything to do with Lua.

If we use a variable watchpoint with a condition using a scope variable,
if we go out-of-scope, the watpoint remains active which can the
expression evaluator to fail to parse the watchpoint condition (because
of the missing varible bindings).

For now, we should disable this test until we come up with a fix for it.

rdar://109574319



Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>