Test CI with JSON@1 (#2864)

Author: odow

docs/Project.toml

@@ -6,5 +6,5 @@ MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
 
 [compat]
 Documenter = "1"
-JSON = "0.21"
+JSON = "1"
 JSONSchema = "1"

docs/src/submodules/FileFormats/overview.md

@@ -282,7 +282,7 @@ Use `JSONSchema.validate` to obtain more insight into why the validation failed:
 julia> JSONSchema.validate(schema, bad_model)
 Validation failed:
 path:         [variables][1]
-instance:     Dict{String, Any}("NaMe" => "x")
+instance:     JSON.Object{String, Any}("NaMe" => "x")
 schema key:   required
 schema value: Any["name"]
 ```