.Net: Bump Npgsql in /dotnet (#9819)

Bumps [Npgsql](https://github.com/npgsql/npgsql).

Updates `Npgsql` from 8.0.5 to 8.0.6
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/npgsql/npgsql/releases">Npgsql's
releases</a>.</em></p>
<blockquote>
<h2>v8.0.6</h2>
<p>The full list of changes is available <a
href="https://github.com/npgsql/npgsql/milestone/121?closed=1">here</a>.</p>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/npgsql/npgsql/compare/v8.0.5...v8.0.6">https://github.com/npgsql/npgsql/compare/v8.0.5...v8.0.6</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/npgsql/npgsql/commit/c4c9d0d53cca12558c5f65c88b3ceb0366bda5e6"><code>c4c9d0d</code></a>
Sync CI macos setup to latest main</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/f5a7042ccf0ff3c546670f3423c2f5a12f5f9d66"><code>f5a7042</code></a>
Stop testing on netcoreapp3.1 (doesn't work on modern mac)</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/3ad6b5dcfaacef42ecdb174b26516c3a01ee024f"><code>3ad6b5d</code></a>
Test tweaks</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/d3a9b183efd47158fc3b670a1fe4cb916fdf1132"><code>d3a9b18</code></a>
Disallow dotnet SDK major version roll forward</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/c6077268e3db7a161a3e4b650102d4b877d1c6e1"><code>c607726</code></a>
Some dependency versions changes to get rid of transitive CVE
errors</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/e1ae4b3d5bd410eed94458a5b6f789de2f29377c"><code>e1ae4b3</code></a>
Bump dotnet SDK to 8.0.404</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/7232c93c33655731969e799406507210db5f530e"><code>7232c93</code></a>
Bump macos version to 15 in CI</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/82c6926bb4a182502769853a3cd2258815adabbd"><code>82c6926</code></a>
Make the default value for json with Json.NET a string (<a
href="https://redirect.github.com/npgsql/npgsql/issues/5914">#5914</a>)</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/882eab96144828053f30212a1bc864d243f1275d"><code>882eab9</code></a>
Fix compilation after e6c166b</li>
<li><a
href="https://github.com/npgsql/npgsql/commit/56688ddf621506ea431e765dafc1b8b55ae57dbf"><code>56688dd</code></a>
Fix not throwing due to overflow while writing NodaTime's period (<a
href="https://redirect.github.com/npgsql/npgsql/issues/5894">#5894</a>)</li>
<li>Additional commits viewable in <a
href="https://github.com/npgsql/npgsql/compare/v8.0.5...v8.0.6">compare
view</a></li>
</ul>
</details>
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</details>

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

dotnet/Directory.Packages.props

@@ -19,7 +19,7 @@
     <PackageVersion Include="Microsoft.VisualStudio.Threading" Version="17.12.19" />
     <PackageVersion Include="MSTest.TestFramework" Version="3.6.1" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
-    <PackageVersion Include="Npgsql" Version="8.0.5" />
+    <PackageVersion Include="Npgsql" Version="8.0.6" />
     <PackageVersion Include="OpenAI" Version="[2.1.0-beta.2]" />
     <PackageVersion Include="Azure.AI.ContentSafety" Version="1.0.0" />
     <PackageVersion Include="Azure.AI.OpenAI" Version="[2.1.0-beta.2]" />