Include <vector> in WatchpointResource.h

On macOS <vector> was already included via another
header file, but this failed on the CI bots.  I'd
tested on linux earlier in this patch's life when
the headers were differently arranged.

(cherry picked from commit a0a1ff3)

Author: jasonmolenda

lldb/include/lldb/Breakpoint/WatchpointResource.h

@@ -13,7 +13,7 @@
 #include "lldb/lldb-public.h"
 
 #include <mutex>
-#include <set>
+#include <vector>
 
 namespace lldb_private {