Update gr_resources.md

added tool assembly in related paged of the Greek covid-19 portal

pages/national_resources/gr_resources.md

@@ -26,7 +26,8 @@ national_resources:
   - name: Greek COVID-19 Portal
     description: Provides information, guidelines, tools and services to support researchers to utilise Greek and European infrastructures for data sharing. The portal is a national node of the European COVID-19 Data Portal.
     url: https://covid19dataportal.gr/
-    related_pages: https://rdmkit.elixir-europe.org/covid19_data_portal
+    related_pages:
+     tool_assembly: [covid19_data_portal]
 
 ref_to_main_resources:
   - argos