Remove BlockHound dependency

The dependency is not needed anymore and there is a issue when using OpenJDK 13 or higher https://github.com/reactor/BlockHound/issues/33

Issue gh-10343

dependencies/spring-security-dependencies.gradle

@@ -27,7 +27,6 @@ dependencies {
 		api "commons-collections:commons-collections:3.2.2"
 		api "commons-logging:commons-logging:1.2"
 		api "io.mockk:mockk:1.12.0"
-		api "io.projectreactor.tools:blockhound:1.0.6.RELEASE"
 		api "javax.annotation:jsr250-api:1.0"
 		api "javax.servlet.jsp.jstl:javax.servlet.jsp.jstl-api:1.2.2"
 		api "javax.servlet.jsp:javax.servlet.jsp-api:2.3.3"

oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/web/reactive/function/client/ServletOAuth2AuthorizedClientExchangeFilterFunctionITests.java

@@ -29,11 +29,9 @@ import javax.servlet.http.HttpServletResponse;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
-import reactor.blockhound.BlockHound;
 import reactor.util.context.Context;
 
 import org.springframework.http.HttpHeaders;
@@ -89,23 +87,6 @@ public class ServletOAuth2AuthorizedClientExchangeFilterFunctionITests {
 
 	private MockHttpServletResponse response;
 
-	@BeforeAll
-	public static void setUpBlockingChecks() {
-		// IMPORTANT:
-		// Before enabling BlockHound, we need to white-list
-		// `java.lang.Class.getPackage()`.
-		// When the JVM loads `java.lang.Package.getSystemPackage()`, it attempts to
-		// `java.lang.Package.loadManifest()` which is blocking I/O and triggers
-		// BlockHound to error.
-		// NOTE: This is an issue with JDK 8. It's been tested on JDK 10 and works fine
-		// w/o this white-list.
-		// @formatter:off
-		BlockHound.builder()
-				.allowBlockingCallsInside(Class.class.getName(), "getPackage")
-				.install();
-		// @formatter:on
-	}
-
 	@BeforeEach
 	public void setUp() throws Exception {
 		this.clientRegistrationRepository = mock(ClientRegistrationRepository.class);