dotcoop2023/Gemfile - workaround - explictly require rdf-rdfxml 3.2.1+

As linkeddata gem doesn't yet require this, we need to. This version
includes a fix for a bug which crashes the `seod generate` step
otherwise.

See ruby-rdf/rdf-rdfxml#40

Also bump se_open_data to 2.1.10

dotcoop2023/Gemfile

@@ -1,2 +1,3 @@
 source "https://rubygems.org"
-gem "se_open_data", :github => "SolidarityEconomyAssociation/se-open-data", :branch => "v2.1.9"
+gem "se_open_data", :github => "SolidarityEconomyAssociation/se-open-data", :branch => "v2.1.10"
+gem "rdf-rdfxml", "~> 3.2", ">= 3.2.1"