Set minimum System.Text.Json version to 5.0.1 (#1923)

Author: LauraArmitage

src/RestSharp/RestSharp.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <ItemGroup Condition="$(TargetFramework) != 'net6.0'">
-        <PackageReference Include="System.Text.Json" Version="[5.0,)" />
+        <PackageReference Include="System.Text.Json" Version="5.0.1" />
     </ItemGroup>
     <ItemGroup>
         <None Remove="RestSharp.csproj.DotSettings" />