board_features: Follow deprecation warnings

This makes the code work both for rdflib 6.1 and 7.0.

doc/rdf/board_features.py

@@ -64,9 +64,9 @@ def colspan(cells: list[Markup]) -> list[Markup]:
     return result
 
 g = rdflib.Graph()
-g.load("features.ttl", format="turtle")
-g.load("info.ttl", format="turtle")
-g.load("terms.ttl", format="turtle")
+g.parse("features.ttl", format="turtle")
+g.parse("info.ttl", format="turtle")
+g.parse("terms.ttl", format="turtle")
 
 boards = g.query("""
         SELECT ?cpuname ?cpu ?cpudoc ?boardname ?board ?boarddoc ?ram ?rom ?wordsizelabel ?architecturelabel ?cpufeaturelabel ?cpufeaturecomment WHERE {