composer.json: bump min. version of rdf-interface and rdf-helpers to 2.0.0

Author: k00ni

composer.json

@@ -18,8 +18,8 @@
         "psr/http-client": "^1.0",
         "halaxa/json-machine": "^1.1.3",
         "guzzlehttp/guzzle": "^7.2",
-        "sweetrdf/rdf-interface": "^1.0.0 | ^2.0.0-RC1",
-        "sweetrdf/rdf-helpers": "^1.0.2"
+        "sweetrdf/rdf-interface": "^2.0.0",
+        "sweetrdf/rdf-helpers": "^2.0.0"
     },
     "suggest": {
         "http-interop/http-factory-guzzle": "^1.0",