fix compiler warnings about using Java `@Deprecated` annotation

[pjfanning]

e.g.

[warn] /Users/pj.fanning/code/incubator-pekko-http/http-core/src/main/scala/org/apache/pekko/http/scaladsl/settings/ServerSettings.scala:142:4: Prefer the Scala annotation over Java's `@Deprecated` to provide a message and version: @deprecated("message", since = "MyLib 1.0")
[warn]   @Deprecated @deprecated("Kept for binary compatibility; Use websocketSettings.withRandomFactoryFactory instead",