update dependencies.

lib/src/kdbx_object.dart

@@ -104,8 +104,7 @@ abstract class KdbxNode with Changeable<KdbxNode> {
   @mustCallSuper
   XmlElement toXml() {
     clean();
-    final el = node.copy() as XmlElement;
-    return el;
+    return node.copy();
   }
 }
 

pubspec.yaml

@@ -13,22 +13,22 @@ dependencies:
   logging: '>=0.11.3+2 <2.0.0'
   crypto: '>=2.0.0 <4.0.0'
   pointycastle: '>=1.0.1 <4.0.0'
-  xml: '>=4.4.0 <5.0.0'
+  xml: '>=4.4.0 <6.0.0'
   uuid: ">=3.0.0 <5.0.0"
   meta: '>=1.0.0 <2.0.0'
   clock: '>=1.0.0 <2.0.0'
   convert: '>=2.0.0 <4.0.0'
   isolate: '>=2.0.3 <3.0.0'
   path: '>=1.6.0 <2.0.0'
-  quiver: '>=2.1.0 <3.0.0'
+  quiver: '>=2.1.0 <4.0.0'
   archive: '>=2.0.13 <4.0.0'
-  supercharged_dart: '>=1.2.0 <2.0.0'
+  supercharged_dart: '>=1.2.0 <4.0.0'
   synchronized: '>=2.2.0 <4.0.0'
 
   collection: '>=1.14.0 <2.0.0'
 
   # required for bin/
-  args: '>1.5.0 <2.0.0'
+  args: '>1.5.0 <3.0.0'
   prompts: '>=1.3.0 <2.0.0'
   logging_appenders: '>=0.1.0 <2.0.0'
   argon2_ffi_base: ^1.0.0