BLD: json deprecated unicode capi
closes #24221

just copying the upstream fix
https://github.com/esnme/ultrajson/commit/ab8f41954a282c67acda7f07a670bb953b98b7c9

Easy enough, but isn't this missing the declaration of new_obj as a point to a PyObject? Nevermind above comment - I see it's intentionally slightly different than upstream fix # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=h1) Report
> Merging [#24254](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9bc42f9d296cf717533051ee76130e72ea9ce557?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24254/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24254   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files         162      162           
  Lines       51768    51768           
=======================================
  Hits        47739    47739           
  Misses       4029     4029
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <ø> (ø)` | :arrow_up: |
| #single | `43% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=footer). Last update [9bc42f9...55c4a40](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=h1) Report
> Merging [#24254](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9bc42f9d296cf717533051ee76130e72ea9ce557?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24254/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24254   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files         162      162           
  Lines       51768    51768           
=======================================
  Hits        47739    47739           
  Misses       4029     4029
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <ø> (ø)` | :arrow_up: |
| #single | `43% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=footer). Last update [9bc42f9...55c4a40](https://codecov.io/gh/pandas-dev/pandas/pull/24254?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @chris-b1 