+doc #20699 improve docs for akka-http (#20722)

Made imports in docs snippets more complete and a few minor improvements

akka-docs/rst/scala/code/docs/http/scaladsl/HttpsExamplesSpec.scala

@@ -9,13 +9,12 @@ import akka.http.scaladsl.Http
 import akka.stream.ActorMaterializer
 import akka.util.ByteString
 import com.typesafe.sslconfig.akka.AkkaSSLConfig
+import docs.CompileOnlySpec
 import org.scalatest.{ Matchers, WordSpec }
 
-class HttpsExamplesSpec extends WordSpec with Matchers {
-
-  "disable SNI for connection" in {
-    pending // compile-time only test
+class HttpsExamplesSpec extends WordSpec with Matchers with CompileOnlySpec {
 
+  "disable SNI for connection" in compileOnlySpec {
     val unsafeHost = "example.com"
     //#disable-sni-connection
     implicit val system = ActorSystem()