finagle-core: Remove Deprecated ServerBuilder.stack Method

Problem / Solution
The `ServerBuilder.stack` method which takes a function has
been deprecated for at least three years. It prevents the `ServerBuilder`
class from being structured in a similar fashion to `ClientBuilder` and
should be removed. This commit removes it.

JIRA Issues: CSL-7377

Differential Revision: https://phabricator.twitter.biz/D251975

CHANGELOG.rst

@@ -41,6 +41,10 @@ Breaking API Changes
   these methods within `TransportContext` should be changed to use the corresponding
   methods on `c.t.f.t.Transport` instead. ``PHAB_ID=D244742``
 
+* finagle-core: The deprecated `c.t.f.b.ServerBuilder.stack` method which takes a function
+  has been removed. Uses of this method should be changed to use the `c.t.f.b.ServerBuilder.stack`
+  method which takes a `c.t.f.s.StackBasedServer` instead. ``PHAB_ID=D251975``
+
 * finagle-core: The deprecated `c.t.f.t.Transport.peerCertificate` method on the `Transport` class
   (not the `Transport.peerCertificate` Finagle context) has been removed. Uses of this
   method should be changed to use `c.t.f.t.TransportContext.peerCertificate` instead.

finagle-core/src/main/scala/com/twitter/finagle/builder/ServerBuilder.scala

@@ -227,22 +227,6 @@ class ServerBuilder[Req, Rep, HasCodec, HasBindTo, HasName] private[builder] (
   def configured[P](paramAndStackParam: (P, Stack.Param[P])): This =
     copy(params.+(paramAndStackParam._1)(paramAndStackParam._2), mk)
 
-  /**
-   * Overrides the stack and [[com.twitter.finagle.Server]] that will be used
-   * by this builder.
-   *
-   * @param mk A function that materializes a `Server` from a set of `Params`.
-   * `mk` is passed the state of configuration when `build` is called. There is
-   * no guarantee that all the builder parameters will be used by the server
-   * created by `mk`; it is up to the discretion of the server and protocol
-   * implementation.
-   */
-  @deprecated("Use stack(server: StackBasedServer)", "7.0.0")
-  def stack[Req1, Rep1](
-    mk: Stack.Params => FinagleServer[Req1, Rep1]
-  ): ServerBuilder[Req1, Rep1, Yes, HasBindTo, HasName] =
-    copy(params, mk)
-
   /**
    * Overrides the stack and [[com.twitter.finagle.Server]] that will be used
    * by this builder.