chore(deps-dev): update pyupgrade requirement from 3.20.0 to 3.21.0 (#896)

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Updates the requirements on
[pyupgrade](https://github.com/asottile/pyupgrade) to permit the latest
version.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/asottile/pyupgrade/commit/f90119b1b8bd9e46949d9592972b2c4c27d62a97"><code>f90119b</code></a>
v3.21.0</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/8a237c945d8f83fa6462643d467a2dfdfa78d779"><code>8a237c9</code></a>
Merge pull request <a
href="https://redirect.github.com/asottile/pyupgrade/issues/1034">#1034</a>
from asottile/py314</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/6f1d9c5b15b2d8e8dfb30d51683966d08f56150a"><code>6f1d9c5</code></a>
regenerate symbols for --py314-plus</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/70fcfb47b4aa54a5aeb16c6430ba51a92718df10"><code>70fcfb4</code></a>
Merge pull request <a
href="https://redirect.github.com/asottile/pyupgrade/issues/1033">#1033</a>
from asottile/pre-commit-ci-update-config</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/5b443e0e90f2a4236eb2b5b6cb5af1eab5b4ac09"><code>5b443e0</code></a>
[pre-commit.ci] pre-commit autoupdate</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/c02489c60a844045bee8dbadd44a0f330f36f7cc"><code>c02489c</code></a>
Merge pull request <a
href="https://redirect.github.com/asottile/pyupgrade/issues/1031">#1031</a>
from asottile/pre-commit-ci-update-config</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/fe2ab3208b4b03c92e3cfb0e3c75deb995dea9fe"><code>fe2ab32</code></a>
[pre-commit.ci] pre-commit autoupdate</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/1b2ebe8c2f425c9d20c5781dd7e5f45e596fa3c2"><code>1b2ebe8</code></a>
Merge pull request <a
href="https://redirect.github.com/asottile/pyupgrade/issues/1029">#1029</a>
from asottile/pre-commit-ci-update-config</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/97f5982c09b2fc8c8e6dd974f1e88e145fff42b1"><code>97f5982</code></a>
[pre-commit.ci] pre-commit autoupdate</li>
<li><a
href="https://github.com/asottile/pyupgrade/commit/7da659f76e1ee206985e666fe3f7ca7cb7096f43"><code>7da659f</code></a>
Merge pull request <a
href="https://redirect.github.com/asottile/pyupgrade/issues/1025">#1025</a>
from asottile/pre-commit-ci-update-config</li>
<li>Additional commits viewable in <a
href="https://github.com/asottile/pyupgrade/compare/v3.20.0...v3.21.0">compare
view</a></li>
</ul>
</details>
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pyproject.toml

@@ -102,7 +102,7 @@ tomli = { version = "2.2.1", python = "<3.11" }
 tox = "4.30.3"
 xmldiff = "2.7.0"
 bandit = "1.8.6"
-pyupgrade = "3.20.0"
+pyupgrade = "3.21.0"
 deptry = "0.23.1"
 # for tests, use the GPL-version of jsonschema format validators - they are faster
 jsonschema = { version = "*", extras = ["format"], optional=true }