Update library to version GitHub recommends

Author: Steve Salas

dotnet-symbol-service/SymbolService/SymbolService.csproj

@@ -10,7 +10,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.5" />
+    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.9" />
     <PackageReference Include="Mono.Cecil" Version="0.10.0-beta7" />
   </ItemGroup>