build(deps): bump ipython from 8.20.0 to 8.21.0 (#543)

Bumps [ipython](https://github.com/ipython/ipython) from 8.20.0 to
8.21.0.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/ipython/ipython/commit/8b1204b6c4489c786ada294088a3acef7bd53e90"><code>8b1204b</code></a>
release 8.21.0</li>
<li><a
href="https://github.com/ipython/ipython/commit/5720ade2c6c742f7618bbbf7950ccefe3939b515"><code>5720ade</code></a>
Whats new 8.21 (<a
href="https://redirect.github.com/ipython/ipython/issues/14315">#14315</a>)</li>
<li><a
href="https://github.com/ipython/ipython/commit/547405393bf17e963b6e6c0315b0fac57d23ec85"><code>5474053</code></a>
Whats new 8.21</li>
<li><a
href="https://github.com/ipython/ipython/commit/5f4d6acd48b4eb3e63354f882b0d607c83f0406a"><code>5f4d6ac</code></a>
Deprecate more complicated way of defining colors. (<a
href="https://redirect.github.com/ipython/ipython/issues/14305">#14305</a>)</li>
<li><a
href="https://github.com/ipython/ipython/commit/dad1cd55c02127e2e355bf78396a64fbeaf00497"><code>dad1cd5</code></a>
Update IPython/utils/coloransi.py</li>
<li><a
href="https://github.com/ipython/ipython/commit/4eab6081807639b6a8322c0a0a19824c047db7f5"><code>4eab608</code></a>
<code>IPython.utils._process_posix</code>: import <code>pexpect</code>
only when needed (<a
href="https://redirect.github.com/ipython/ipython/issues/14312">#14312</a>)</li>
<li><a
href="https://github.com/ipython/ipython/commit/643c75d0c3f7558874ad8fb8f6164ebaa3026728"><code>643c75d</code></a>
pyproject.toml, setup.py: Declare backend-path (<a
href="https://redirect.github.com/ipython/ipython/issues/14313">#14313</a>)</li>
<li><a
href="https://github.com/ipython/ipython/commit/a069d99eb53328d5742535b2597619f1e2c04eb0"><code>a069d99</code></a>
Prepare removal of unnecessary options of ColorSchemeTable. (<a
href="https://redirect.github.com/ipython/ipython/issues/14307">#14307</a>)</li>
<li><a
href="https://github.com/ipython/ipython/commit/c928806ce58316f0cec2d3a020f6d342f9510395"><code>c928806</code></a>
pyproject.toml, setup.py: Declare backend-path</li>
<li><a
href="https://github.com/ipython/ipython/commit/93ffc153525ffa66e5165b3e6866657811d04ce4"><code>93ffc15</code></a>
Remove old mentions and uses of ipython_extension_dir (<a
href="https://redirect.github.com/ipython/ipython/issues/14310">#14310</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/ipython/ipython/compare/8.20.0...8.21.0">compare
view</a></li>
</ul>
</details>
<br />


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Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>