Add link to explain blivet-gui 'workaround' needle

Add a link to the issue report for blivet-gui using an odd icon
for btrfs volumes, now I finally filed it.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/anaconda/partitioning/blivet/anaconda_blivet_volumes_icon-folder-20220920.json

@@ -11,10 +11,10 @@
   "properties": [
     {
       "name": "workaround",
-      "value": "this icon should not be a folder"
+      "value": "this icon should not be a folder - https://github.com/storaged-project/blivet-gui/issues/398"
     }
   ],
   "tags": [
     "anaconda_blivet_volumes_icon"
   ]
-}
+}

needles/anaconda/partitioning/blivet/anaconda_blivet_volumes_icon-folder-20230222.json

@@ -11,10 +11,10 @@
   "properties": [
     {
       "name": "workaround",
-      "value": "this icon should not be a folder"
+      "value": "this icon should not be a folder - https://github.com/storaged-project/blivet-gui/issues/398"
     }
   ],
   "tags": [
     "anaconda_blivet_volumes_icon"
   ]
-}
+}