Ensure we have XP framework core >= 9.1.0

Includes fix for casting lang.XPClass::newInstance() via function types
See xp-framework/core#183

Author: thekid

composer.json

@@ -6,7 +6,7 @@
   "description" : "REST Client and Server APIs for the XP Framework",
   "keywords": ["module", "xp"],
   "require" : {
-    "xp-framework/core": "^9.0 | ^8.0 | ^7.0 | ^6.5",
+    "xp-framework/core": "^9.1 | ^8.0 | ^7.0 | ^6.5",
     "xp-framework/http": "^9.0 | ^8.0 | ^7.0 | ^6.2",
     "xp-framework/xml": "^9.0 | ^8.0 | ^7.0 | ^6.0",
     "xp-framework/scriptlet": "^9.0 | ^8.0.1",