tmf.core: Deprecate the unused AREA DisplayType

As this type can always be brought back, alongside actual usage of it.

[Deprecated] Unused o.e.t.t.core.model.xy.ISeriesModel.DisplayType.AREA

Change-Id: I6efb1921241e8cc9b8df09f2a3b87760f302ec5f
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass/org.eclipse.tracecompass/+/193161
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>

tmf/org.eclipse.tracecompass.tmf.core/src/org/eclipse/tracecompass/tmf/core/model/xy/ISeriesModel.java

@@ -43,7 +43,10 @@ public enum DisplayType {
         SCATTER,
         /**
          * Area
+         *
+         * @deprecated As currently unused, at least in o.e.tracecompass.
          */
+        @Deprecated
         AREA
     }