Remove Spring Security OAuth Auto-Configuration

This commit removes auto-configuration support for Spring Security
OAuth, paving the way for the introduction of auto-configuration for
Spring Security 5's new OAuth-related features.

Closes gh-10255

spring-boot-cli/samples/oauth2.groovy

@@ -1,13 +0,0 @@
-package org.test
-
-@EnableAuthorizationServer
-@EnableResourceServer
-@RestController
-class SampleController {
-
-	@RequestMapping("/")
-	def hello() {
-		[message: "Hello World!"]
-	}
-
-}