Bump polars from 0.18.3 to 0.18.4 (#464)

Bumps [polars](https://github.com/pola-rs/polars) from 0.18.3 to 0.18.4.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/pola-rs/polars/commit/5ee93f42cc058c8c2ab6b20876ffc5f39e23b665"><code>5ee93f4</code></a>
python polars 0.18.4 (<a
href="https://redirect.github.com/pola-rs/polars/issues/9524">#9524</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/6a43638936fde807e39604600d8fe78daeaa1958"><code>6a43638</code></a>
fix(python): ensure that trying to use a string as a dtype raises a
consisten...</li>
<li><a
href="https://github.com/pola-rs/polars/commit/12fa710cd4c912cfd8e86d684d300914e841dfb0"><code>12fa710</code></a>
refactor(python, rust): don't pickle pyarrow dataset (<a
href="https://redirect.github.com/pola-rs/polars/issues/9523">#9523</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/e3a09428a4810289d89a6310cad853dd0ce70d49"><code>e3a0942</code></a>
fix(rust, python): fix race condition in out-of-core sort (<a
href="https://redirect.github.com/pola-rs/polars/issues/9521">#9521</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/584849c6222fa04842202d4066e4aadc08ff8541"><code>584849c</code></a>
fix(rust, python): unset sortedness for local date and local datetime
(<a
href="https://redirect.github.com/pola-rs/polars/issues/9515">#9515</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/51111752066b4ef34e117e9d63a409e530fd347e"><code>5111175</code></a>
chore: update arrow (<a
href="https://redirect.github.com/pola-rs/polars/issues/9514">#9514</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/373a99a33dd568e321adb8a31404c97380333817"><code>373a99a</code></a>
feat(python,rust): add drop_first parameter for to_dummies (issue <a
href="https://redirect.github.com/pola-rs/polars/issues/8246">#8246</a>)
(<a
href="https://redirect.github.com/pola-rs/polars/issues/9">#9</a>...</li>
<li><a
href="https://github.com/pola-rs/polars/commit/c670555cf5619bce06d4fe4da102be7e093a959c"><code>c670555</code></a>
fix(rust, python): maintain sortedness flags on append/extend (<a
href="https://redirect.github.com/pola-rs/polars/issues/9496">#9496</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/f94abbbf87034d37a6f9f7d2b856c327a5d79417"><code>f94abbb</code></a>
chore(python): fix test failing CI (<a
href="https://redirect.github.com/pola-rs/polars/issues/9509">#9509</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/9e501f9ce6128283454783348e4cd759a1c34918"><code>9e501f9</code></a>
fix(rust, python): fix serde for small integer dtypes (<a
href="https://redirect.github.com/pola-rs/polars/issues/9495">#9495</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/pola-rs/polars/compare/py-0.18.3...py-0.18.4">compare
view</a></li>
</ul>
</details>
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</details>

Author: llucax

pyproject.toml

@@ -58,7 +58,7 @@ docs-lint = [
 ]
 format = ["black == 23.3.0", "isort == 5.12.0"]
 nox = ["nox == 2023.4.22", "toml == 0.10.2"]
-examples = [ "polars == 0.18.3" ]
+examples = [ "polars == 0.18.4" ]
 pytest = [
   "pytest == 7.3.2",
   "pytest-cov == 4.1.0",