Fix data_type ctor call in JSON_TEST (#17273)

Fixes call to `data_type{}` ctor in `json_test.cpp`. The 2-parameter ctor is for fixed-point-types only and will assert in a debug build if used incorrectly: https://github.com/rapidsai/cudf/blob/2db58d58b4a986c2c6fad457f291afb1609fd458/cpp/include/cudf/types.hpp#L277-L280

Partial stack trace from a gdb run
```
#5  0x000077b1530bc71b in __assert_fail_base (fmt=0x77b153271130 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
    assertion=0x58c3e4baaa98 "id == type_id::DECIMAL32 || id == type_id::DECIMAL64 || id == type_id::DECIMAL128",
    file=0x58c3e4baaa70 "/cudf/cpp/include/cudf/types.hpp", line=279, function=<optimized out>) at ./assert/assert.c:92
#6  0x000077b1530cde96 in __GI___assert_fail (
    assertion=0x58c3e4baaa98 "id == type_id::DECIMAL32 || id == type_id::DECIMAL64 || id == type_id::DECIMAL128",
    file=0x58c3e4baaa70 "/cudf/cpp/include/cudf/types.hpp", line=279, function=0x58c3e4baaa38 "cudf::data_type::data_type(cudf::type_id, int32_t)")
    at ./assert/assert.c:101
#7  0x000058c3e48ba594 in cudf::data_type::data_type (this=0x7fffdd3f7530, id=cudf::type_id::STRING, scale=0) at /cudf/cpp/include/cudf/types.hpp:279
#8  0x000058c3e49215d9 in JsonReaderTest_MixedTypesWithSchema_Test::TestBody (this=0x58c3e5ea13a0) at /cudf/cpp/tests/io/json/json_test.cpp:2887

```

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Karthikeyan (https://github.com/karthikeyann)
  - Muhammad Haseeb (https://github.com/mhaseeb123)

URL: #17273

cpp/tests/io/json/json_test.cpp

@@ -2885,9 +2885,9 @@ TEST_F(JsonReaderTest, MixedTypesWithSchema)
   std::map<std::string, cudf::io::schema_element> data_types;
   std::map<std::string, cudf::io::schema_element> child_types;
   child_types.insert(
-    std::pair{"element", cudf::io::schema_element{cudf::data_type{cudf::type_id::STRING, 0}, {}}});
-  data_types.insert(std::pair{
-    "data", cudf::io::schema_element{cudf::data_type{cudf::type_id::LIST, 0}, child_types}});
+    std::pair{"element", cudf::io::schema_element{cudf::data_type{cudf::type_id::STRING}, {}}});
+  data_types.insert(
+    std::pair{"data", cudf::io::schema_element{cudf::data_type{cudf::type_id::LIST}, child_types}});
 
   cudf::io::json_reader_options in_options =
     cudf::io::json_reader_options::builder(cudf::io::source_info{data.data(), data.size()})