build: Back down FluentAssertions to 5.9

5.10 has Task type conflict issues I don't feel like resolving.

Author: qdot

Buttplug.Client.Connectors.WebsocketConnector.Test/Buttplug.Client.Connectors.WebsocketConnector.Test.csproj

@@ -35,8 +35,8 @@
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="FluentAssertions, Version=5.10.3.0, Culture=neutral, PublicKeyToken=33f2691a05b67b6a, processorArchitecture=MSIL">
-      <HintPath>..\packages\FluentAssertions.5.10.3\lib\net47\FluentAssertions.dll</HintPath>
+    <Reference Include="FluentAssertions, Version=5.9.0.0, Culture=neutral, PublicKeyToken=33f2691a05b67b6a, processorArchitecture=MSIL">
+      <HintPath>..\packages\FluentAssertions.5.9.0\lib\net47\FluentAssertions.dll</HintPath>
     </Reference>
     <Reference Include="Namotion.Reflection, Version=1.0.12.0, Culture=neutral, PublicKeyToken=c2f9c3bdfae56102, processorArchitecture=MSIL">
       <HintPath>..\packages\Namotion.Reflection.1.0.12\lib\net45\Namotion.Reflection.dll</HintPath>

Buttplug.Client.Connectors.WebsocketConnector.Test/packages.config

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="FluentAssertions" version="5.10.3" targetFramework="net47" />
+  <package id="FluentAssertions" version="5.9.0" targetFramework="net47" />
   <package id="Namotion.Reflection" version="1.0.12" targetFramework="net47" />
   <package id="Newtonsoft.Json" version="12.0.3" targetFramework="net47" />
   <package id="NJsonSchema" version="10.1.21" targetFramework="net47" />

Buttplug.Test/Buttplug.Test.csproj

@@ -13,7 +13,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="5.10.3" />
+    <PackageReference Include="FluentAssertions" Version="5.9.0" />
     <PackageReference Include="NLog" Version="4.7.2" />
     <PackageReference Include="nunit" Version="3.12.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.6.1" />