Removing references to SCM2 also from docs #358 (review)

Author: jglick

docs/implementation.adoc

@@ -1466,7 +1466,6 @@ Auto-registration of webhooks is performed in different methods depending on the
 
 * `SCMNavigator.afterSave(_owner_)`
 * `SCMSource.afterSave()`
-* `SCM2.afterSave(_job_)`
 
 In the above methods you need to register the webhook url using your SCM Provider API to which Jenkins will listen for events.
 
@@ -1483,17 +1482,6 @@ public String getHookUrl() {
 }
 ----
 
-[NOTE]
-====
-Existing implementations of the `hudson.scm.SCM` API have traditionally extended `hudson.triggers.Trigger` in order to integrate capture the requirement for setting up a webhook from the `Trigger.start(_job_,_newInstance_)` method.
-
-This leads to a proliferation of triggers for multiple source control systems and consequently confuses users and leads to a bad user experience.
-
-Switching those implementations to use `SCM2.afterSave(_job_,_scm_)` will result in a simpler user interface of just enabling _Poll SCM_ and managing the hooks through _Ignore post-commit hooks_.
-
-Additionally, unless a source control system can guarantee delivery of events, in order to ensure that events are not lost, users will need to configure _Poll SCM_ in any case (even if only with the schedule of `@yearly`!)
-====
-
 [TIP]
 ====
 If you are implementing auto-registration of webhooks, keep a local database of what hooks have been attempted to be registered.