Update Twilio package to version 6.18.0 (#916)

src/WebJobs.Extensions.Twilio/WebJobs.Extensions.Twilio.csproj

@@ -23,7 +23,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.Azure.WebJobs" Version="3.0.41" />
     <PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="6.34.0" />
-    <PackageReference Include="Twilio" Version="6.2.5" />
+    <PackageReference Include="Twilio" Version="6.18.0" />
   </ItemGroup>
 
   <ItemGroup>