Fix data_type ctor call in JSON_TEST

[davidwendt]

Description

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:

cudf/cpp/include/cudf/types.hpp

Lines 277 to 280 in 2db58d5

	explicit data_type(type_id id, int32_t scale) : _id{id}, _fixed_point_scale{scale}
	{
	assert(id == type_id::DECIMAL32 || id == type_id::DECIMAL64 || id == type_id::DECIMAL128);
	}

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

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[karthikeyann]

Thank you for fixing this.
LGTM 👍

[davidwendt]

/merge