Remove field 'display_label_linkable' from 'external_db' table.

sql/patch_61_62_d.sql

+# patch_61_62_d.sql
+#
+# Title: Remove field display_label_linkable from external_db table.
+#
+# Description:
+# Field is obsolete.
+
+ALTER TABLE external_db DROP display_label_linkable;
+
+# Patch identifier
+INSERT INTO meta (species_id, meta_key, meta_value)
+  VALUES (NULL, 'patch', 'patch_61_62_d.sql|remove_display_label_linkable');