Error when converting df to json table (utc timezone date time object causes the error)
When converting df.to_json(orient="table",index=False)
and there are datetime.now(timezone.utc) objects in the table it causes the following error (Without orient table it works though.): 


`---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-122-4a9c9a4c89de> in <module>
----> 1 x = current_opportunites.to_json(orient="table",index=False)

/opt/conda/lib/python3.8/site-packages/pandas/core/generic.py in to_json(self, path_or_buf, orient, date_format, double_precision, force_ascii, date_unit, default_handler, lines, compression, index, indent, storage_options)
   2463         indent = indent or 0
   2464 
-> 2465         return json.to_json(
   2466             path_or_buf=path_or_buf,
   2467             obj=self,

/opt/conda/lib/python3.8/site-packages/pandas/io/json/_json.py in to_json(path_or_buf, obj, orient, date_format, double_precision, force_ascii, date_unit, default_handler, lines, compression, index, indent, storage_options)
     83         raise NotImplementedError("'obj' should be a Series or a DataFrame")
     84 
---> 85     s = writer(
     86         obj,
     87         orient=orient,

/opt/conda/lib/python3.8/site-packages/pandas/io/json/_json.py in __init__(self, obj, orient, date_format, double_precision, ensure_ascii, date_unit, index, default_handler, indent)
    249             raise ValueError(msg)
    250 
--> 251         self.schema = build_table_schema(obj, index=self.index)
    252 
    253         # NotImplemented on a column MultiIndex

/opt/conda/lib/python3.8/site-packages/pandas/io/json/_table_schema.py in build_table_schema(data, index, primary_key, version)
    261     if data.ndim > 1:
    262         for column, s in data.items():
--> 263             fields.append(convert_pandas_type_to_json_field(s))
    264     else:
    265         fields.append(convert_pandas_type_to_json_field(data))

/opt/conda/lib/python3.8/site-packages/pandas/io/json/_table_schema.py in convert_pandas_type_to_json_field(arr)
    122         field["freq"] = dtype.freq.freqstr
    123     elif is_datetime64tz_dtype(dtype):
--> 124         field["tz"] = dtype.tz.zone
    125     return field
    126 

AttributeError: 'datetime.timezone' object has no attribute 'zone'`

https://github.com/pandas-dev/pandas/blob/d3788525ee368db0b6565b72ab4eeba9140fd1d4/pandas/io/json/_table_schema.py#L123


Will have a deeper look later.
