Use the snippet-generator redirect

Allows the description of the snippet generator to move on the
jenkins.io site without requiring a change in the plugin source code.

Depends on jenkins-infra/jenkins.io#4133

Author: MarkEWaite

README.md

@@ -79,7 +79,7 @@ The `checkout` step may be used to run any other SCM plugin, provided that it ha
 It could also be used to run an SCM for which there is a special integration that lacks support for an exotic feature.
 The step takes an `scm` parameter which is a map containing at least a `$class` parameter giving the full or simple class name of the desired `SCM` implementation, and the standard `poll` and `changelog` parameters.
 
-It also takes any other parameters supported by the SCM plugin in its configuration form, using their internal names and values; use _Snippet Generator_ to get a detailed example for your SCM.
+It also takes any other parameters supported by the SCM plugin in its configuration form, using their internal names and values; use [_Snippet Generator_](https://jenkins.io/redirect/pipeline-snippet-generator)to get a detailed example for your SCM.
 Optional parameters can be omitted and will take their default values (to the extent supported by the SCM plugin).
 For example, to run Mercurial (1.51-beta-2 or higher):
 

src/main/resources/org/jenkinsci/plugins/workflow/steps/scm/GenericSCMStep/help.jelly

@@ -5,9 +5,9 @@
     This is a special step that will checkout using the configuration
     options offered by any Pipeline-compatible SCM plugin.
     Install the corresponding SCM plugin and select it from the list in the
-    <strong><a href="https://jenkins.io/doc/book/pipeline/getting-started/#snippet-generator">Pipeline Snippet Generator</a></strong>.
+    <strong><a href="https://jenkins.io/redirect/pipeline-snippet-generator">Pipeline Snippet Generator</a></strong>.
     The
-    <strong><a href="https://jenkins.io/doc/book/pipeline/getting-started/#snippet-generator">Pipeline Snippet Generator</a></strong>
+    <strong><a href="https://jenkins.io/redirect/pipeline-snippet-generator">Pipeline Snippet Generator</a></strong>
     uses the installed SCM plugins of your Jenkins server to suggest pipeline snippets.
     </p>
     <p>This step returns a <code>Map</code> of any variables the SCM plugin would