upgrade dependencies.

pubspec.yaml

@@ -12,18 +12,18 @@ dependencies:
 #  path: ^1.6.0
   logging: '>=0.11.3+2 <2.0.0'
   crypto: '>=2.0.0 <4.0.0'
-  pointycastle: '>=1.0.1 <3.0.0'
+  pointycastle: '>=1.0.1 <4.0.0'
   xml: '>=4.4.0 <5.0.0'
   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 <3.0.0'
+  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'
   archive: '>=2.0.13 <4.0.0'
   supercharged_dart: '>=1.2.0 <2.0.0'
-  synchronized: '>=2.2.0 <3.0.0'
+  synchronized: '>=2.2.0 <4.0.0'
 
   collection: '>=1.14.0 <2.0.0'