[lldb] [NFC] Remove unused WatchpointResourceList class (#79385)

In `[lldb] [mostly NFC] Large WP foundation: WatchpointResources
(#68845)` I added a new template StopPointSiteList to combine
WatchpointResourceList and BreakpointSiteList. But I didn't remove the
now-unused WatchpointResourceList class. This patch fixes that.

Author: jasonmolenda

lldb/include/lldb/Breakpoint/WatchpointResourceList.h

@@ -24,7 +24,6 @@ add_lldb_library(lldbBreakpoint NO_PLUGIN_DEPENDENCIES
   WatchpointList.cpp
   WatchpointOptions.cpp
   WatchpointResource.cpp
-  WatchpointResourceList.cpp
 
   LINK_LIBS
     lldbCore