Bump polars from 0.18.8 to 0.18.9 (#553)

Bumps [polars](https://github.com/pola-rs/polars) from 0.18.8 to 0.18.9.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/pola-rs/polars/commit/c1f5dc23b40a5b047390e9821074963fe167756b"><code>c1f5dc2</code></a>
python polars 0.18.9 (<a
href="https://redirect.github.com/pola-rs/polars/issues/10144">#10144</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/78b51e38a3bd29918230e2bb7423c70c8d8a724e"><code>78b51e3</code></a>
chore(rust): update to rustc nightly-2023-07-27 (<a
href="https://redirect.github.com/pola-rs/polars/issues/10139">#10139</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/8937f0386628ab93657323791c6d10126ec378c1"><code>8937f03</code></a>
chore(python): get test_udfs running on all python versions again (<a
href="https://redirect.github.com/pola-rs/polars/issues/10136">#10136</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/6f50fb8ff53fb1a29f3c94479f1a199a1bc38452"><code>6f50fb8</code></a>
depr(python): Deprecate parsing string inputs as literals for
`when-then-othe...</li>
<li><a
href="https://github.com/pola-rs/polars/commit/4381c04fb9302d235141c3899e6441fcfc113fb4"><code>4381c04</code></a>
depr(python): deprecate &quot;connection_uri&quot; →
&quot;connection&quot; param in read/write d...</li>
<li><a
href="https://github.com/pola-rs/polars/commit/3881d3d45dae19f253532e40420110dd7537bca2"><code>3881d3d</code></a>
ci: temporarily turn off fail-fast so that ubuntu tests run (<a
href="https://redirect.github.com/pola-rs/polars/issues/10133">#10133</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/9ff9b0a68aa536ac0d48d1abdb58760d6e32e45a"><code>9ff9b0a</code></a>
feat(python): suggest map_dict instead of lambda x: DICT[x] (<a
href="https://redirect.github.com/pola-rs/polars/issues/10123">#10123</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/f27c9b7ab880bc2e4eaa96b23c866c5b62d45e24"><code>f27c9b7</code></a>
fix(rust, python): adjust for null values in str.replace fast path (<a
href="https://redirect.github.com/pola-rs/polars/issues/10132">#10132</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/a20724158a05fd86eaffa092447a44d1e7a1fbfc"><code>a207241</code></a>
fix(rust, python): clear bit settings in list iteration (<a
href="https://redirect.github.com/pola-rs/polars/issues/10131">#10131</a>)</li>
<li><a
href="https://github.com/pola-rs/polars/commit/28dad4dc9eb7836652294a2ec27b0f419b9357c6"><code>28dad4d</code></a>
fix(rust, python): use row-encoded for struct::is_sorted (<a
href="https://redirect.github.com/pola-rs/polars/issues/10129">#10129</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/pola-rs/polars/compare/py-0.18.8...py-0.18.9">compare
view</a></li>
</ul>
</details>
<br />

[![Dependabot compatibility
score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=polars&package-manager=pip&previous-version=0.18.8&new-version=0.18.9)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Dependabot will resolve any conflicts with this PR as long as you don't
alter it yourself. You can also trigger a rebase manually by commenting
`@dependabot rebase`.

[//]: # (dependabot-automerge-start)
[//]: # (dependabot-automerge-end)

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits
that have been made to it
- `@dependabot merge` will merge this PR after your CI passes on it
- `@dependabot squash and merge` will squash and merge this PR after
your CI passes on it
- `@dependabot cancel merge` will cancel a previously requested merge
and block automerging
- `@dependabot reopen` will reopen this PR if it is closed
- `@dependabot close` will close this PR and stop Dependabot recreating
it. You can achieve the same result by closing it manually
- `@dependabot ignore this major version` will close this PR and stop
Dependabot creating any more for this major version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this minor version` will close this PR and stop
Dependabot creating any more for this minor version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this dependency` will close this PR and stop
Dependabot creating any more for this dependency (unless you reopen the
PR or upgrade to it yourself)

</details>

Author: daniel-zullo-frequenz

pyproject.toml

@@ -54,7 +54,7 @@ dev-docstrings = [
   "darglint == 1.8.1",
   "tomli == 2.0.1",      # Needed by pydocstyle to read pyproject.toml
 ]
-dev-examples = ["polars == 0.18.8"]
+dev-examples = ["polars == 0.18.9"]
 dev-formatting = ["black == 23.7.0", "isort == 5.12.0"]
 dev-mkdocs = [
   "mike == 1.1.2",