Update docs

- Remove and fix content with wrong links.
- Relates #433

Author: jvalkeal

spring-shell-docs/src/main/asciidoc/using-shell-components-builtin.adoc

@@ -1,11 +1,6 @@
 [[built-in-commands]]
 ==== Built-In Commands
 
-Any application built by using the `{starter-artifactId}` artifact
-(which equates to the `spring-shell-standard-commands` dependency) comes with a set of built-in commands.
-You can override or disable these commands individually (see <<overriding-or-disabling-built-in-commands>>).
-However, if they are not overridden or disabled, this section describes their behavior.
-
 [[help-command]]
 ===== Help
 
@@ -92,7 +87,7 @@ in the top left corner.
 
 The `quit` command (also aliased as `exit`) requests the shell to quit, gracefully
 closing the Spring application context. If not overridden, a JLine `History` bean writes a history of all
-commands to disk, so that they are available again (see <<interacting-with-the-shell>>) on the next launch.
+commands to disk, so that they are available again on the next launch.
 
 ===== Stacktrace
 

spring-shell-docs/src/main/asciidoc/using-shell-customization.adoc

@@ -3,6 +3,4 @@
 
 This section describes how you can customize the shell.
 
-include::using-shell-customization-generic.adoc[]
-
 include::using-shell-customization-styling.adoc[]

spring-shell-docs/src/main/asciidoc/using-shell-options-validation.adoc

@@ -26,11 +26,3 @@ The following constraints were not met:
 	--password string : size must be between 8 and 40 (You passed 'hello')
 ----
 ====
-
-[NOTE]
-.Applies to All Command Implementations
-====
-It is important to note that bean validation applies to all command implementations,
-whether they use the "`standard`" API or any other API, through the use of an adapter
-(see <<support-for-shell-1-and-jcommander,Supporting Other APIs>>).
-====