Add missing deprecation annotation

Author: mrotteveel

src/main/org/firebirdsql/management/FBBackupManagerBase.java

@@ -55,6 +55,7 @@ public String getPath() {
         /**
          * @deprecated use {@link #size()}; this method may be removed in Jaybird 8 or later
          */
+        @Deprecated(since = "7", forRemoval = true)
         public int getSize() {
             return size;
         }