chore: removed Specialized dependency

Author: sbansla

src/Twilio/Twilio.csproj

@@ -40,7 +40,6 @@
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="8.3.1" />
     <PackageReference Include="Microsoft.IdentityModel.Tokens" Version="8.3.1" />
-    <PackageReference Include="System.Collections.Specialized" Version="4.3.0" />
   </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.1' ">
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />