util/generate-hugo-content.py: controlled vocabularies

We are planning to remove the controlled vocabularies from the CSV
files so we should not expect that this column will exist. Instead,
check if there is a controlled vocabulary in the data directory.

The controlled vocabularies were already exported once using the
util/export-controlled-vocabularies.py script so we don't actually
need them in the CSVs anymore.

util/generate-hugo-content.py

@@ -90,7 +90,7 @@ def parseSchema(schema_df):
         cardinality = row["element options"].capitalize()
         prop_type = row["element type"].capitalize()
 
-        if row["element controlled values or terms"]:
+        if os.path.isfile(f"data/controlled-vocabularies/{element_name_safe}.txt"):
             controlled_vocab = True
 
             controlled_vocabulary_src = (