Update axum requirement from 0.5.1 to 0.6.20 (#514)

Updates the requirements on [axum](https://github.com/tokio-rs/axum) to
permit the latest version.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/tokio-rs/axum/releases">axum's
releases</a>.</em></p>
<blockquote>
<h2>axum - v0.6.20</h2>
<ul>
<li><strong>added:</strong>
<code>WebSocketUpgrade::write_buffer_size</code> and
<code>WebSocketUpgrade::max_write_buffer_size</code></li>
<li><strong>changed:</strong> Deprecate
<code>WebSocketUpgrade::max_send_queue</code></li>
<li><strong>change:</strong> Update tokio-tungstenite to 0.20</li>
<li><strong>added:</strong> Implement <code>Handler</code> for <code>T:
IntoResponse</code> (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2140">#2140</a>)</li>
</ul>
<p><a
href="https://redirect.github.com/tokio-rs/axum/issues/2140">#2140</a>:
<a
href="https://redirect.github.com/tokio-rs/axum/pull/2140">tokio-rs/axum#2140</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/tokio-rs/axum/commit/3b92cd7593a900d3c79c2aeb411f90be052a9a5c"><code>3b92cd7</code></a>
Release axum and axum-extra (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2145">#2145</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/68333b2fcfb5ae657f3e8c8a5850e09197ba9e3a"><code>68333b2</code></a>
Backport changes from main to v0.6.x (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2141">#2141</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/a25ed293d75aebc1ce7ea3500c88d7d88e669e5e"><code>a25ed29</code></a>
axum-extra 0.7.6 (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2139">#2139</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/990cbb8126ed88d8642cc5096fddc69577fa6095"><code>990cbb8</code></a>
Update tokio-tungstenite 0.20 (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2123">#2123</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/a2916318ddadf6bd27344aaa918194ad497318dc"><code>a291631</code></a>
axum-extra: Remove unused tower-http dependency (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2135">#2135</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/67f64943831c288f1434c7dee7e732e3f86bda69"><code>67f6494</code></a>
Release axum 0.6.19 (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2102">#2102</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/2d4bd9e85380cfc6faf3e672b6cee892bccfce3d"><code>2d4bd9e</code></a>
Update to latest sqlx in example (<a
href="https://redirect.github.com/tokio-rs/axum/issues/2099">#2099</a>)</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/e881bf0aeca5b4a7068ce82fc48422fca14f9212"><code>e881bf0</code></a>
Update UI tests</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/5d9f41edf37d0b70103eb4f37340d52f62fa3719"><code>5d9f41e</code></a>
Fix deny.toml</li>
<li><a
href="https://github.com/tokio-rs/axum/commit/19ddc12e4e1215f15adea505beee4ba6be8c8d75"><code>19ddc12</code></a>
Remove sessions example</li>
<li>Additional commits viewable in <a
href="https://github.com/tokio-rs/axum/compare/axum-v0.5.1...axum-v0.6.20">compare
view</a></li>
</ul>
</details>
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testimages/Cargo.toml

@@ -6,7 +6,7 @@ publish = false
 
 [dependencies]
 anyhow = "1.0.56"
-axum = { version = "0.5.1", features = [ "http2" ] }
+axum = { version = "0.6.20", features = [ "http2" ] }
 tokio = { version = "1.17.0", features = [ "full" ] }
 
 [build-dependencies]