fix: added migration to import the participating municipalities

The original migration to import the participants for public OCMW associations
contained a bug causing it to not match municipalities. More specifically:
- the type triple for municipalities is located in the `shared` graph;
- consequently the `FILTER EXISTS` statements to limit matches to administrative
  units could not succeed for municipalities as the queries are limited to the
  `administrative-unit` graph.

This new migration fixes this problem by changing the `FILTER EXISTS` into a
`FILTER NOT EXISTS` to exclude resourses of type `ext:KboOrganisatie`.

config/dev-migrations/20240522095345-public-ocmw-associations-remov-participants.sparql

@@ -1,16 +0,0 @@
-PREFIX org: <http://www.w3.org/ns/org#>
-
-DELETE {
-  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
-    ?participant org:memberOf ?association .
-  }
-} WHERE {
-  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
-    ?participant org:memberOf ?association .
-    ?association org:classification ?class
-  }
-  VALUES ?class {
-    <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/e8294b73-87c9-4fa2-9441-1937350763c9> # Welzijnsvereniging
-        <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/34b5af85-dc9f-468f-9e03-ef89b174c267> # Autonome verzorgingsinstelling
-  }
-}

config/migrations/20240619123310-remove-kbo-organizations-from-participation-relation.sparql

@@ -0,0 +1,13 @@
+PREFIX org: <http://www.w3.org/ns/org#>
+PREFIX ext: <http://mu.semte.ch/vocabularies/ext/>
+
+DELETE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?participant org:memberOf ?association .
+  }
+} WHERE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?participant org:memberOf ?association .
+    ?association a ext:KboOrganisatie .
+  }
+}