Remove deprecated get(Set-Cookie) on headers

core/src/main/scala/org/http4s/Headers.scala

@@ -42,13 +42,6 @@ final class Headers private (private val headers: List[Header]) extends AnyVal {
     */
   def get(key: HeaderKey.Extractable): Option[key.HeaderT] = key.from(this)
 
-  @deprecated(
-    "Use response.cookies instead. Set-Cookie is unique among HTTP headers in that it can be repeated but can't be joined by a ','. This will return only the first Set-Cookie header. `response.cookies` will return the complete list.",
-    "0.16.0-RC1"
-  )
-  def get(key: `Set-Cookie`.type): Option[`Set-Cookie`] =
-    key.from(this).headOption
-
   /** Attempt to get a [[org.http4s.Header]] from this collection of headers
     *
     * @param key name of the header to find