fix: CandidateParam类型应为String

Author: LesanOuO

src/components/bpmnProcessDesigner/package/designer/plugins/descriptor/flowableDescriptor.json

@@ -1409,7 +1409,7 @@
       "properties": [
         {
           "name": "value",
-          "type": "Integer",
+          "type": "String",
           "isBody": true
         }
       ]