Remove BlockHound dependency

Since it is not yet GA

Fixes gh-7220

gradle/dependency-management.gradle

@@ -70,7 +70,6 @@ dependencyManagement {
 		dependency 'commons-lang:commons-lang:2.6'
 		dependency 'commons-logging:commons-logging:1.2'
 		dependency 'dom4j:dom4j:1.6.1'
-		dependency 'io.projectreactor.tools:blockhound:1.0.0.M4'
 		dependency 'javax.activation:activation:1.1.1'
 		dependency 'javax.annotation:jsr250-api:1.0'
 		dependency 'javax.inject:javax.inject:1'

oauth2/oauth2-client/spring-security-oauth2-client.gradle

@@ -17,7 +17,6 @@ dependencies {
 	testCompile 'com.fasterxml.jackson.core:jackson-databind'
 	testCompile 'io.projectreactor.netty:reactor-netty'
 	testCompile 'io.projectreactor:reactor-test'
-	testCompile 'io.projectreactor.tools:blockhound'
 
 	provided 'javax.servlet:javax.servlet-api'
 }

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

@@ -19,7 +19,6 @@ import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import org.junit.After;
 import org.junit.Before;
-import org.junit.BeforeClass;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
 import org.springframework.http.HttpHeaders;
@@ -42,7 +41,6 @@ import org.springframework.security.oauth2.core.TestOAuth2RefreshTokens;
 import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.context.request.ServletRequestAttributes;
 import org.springframework.web.reactive.function.client.WebClient;
-import reactor.blockhound.BlockHound;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -70,18 +68,6 @@ public class ServletOAuth2AuthorizedClientExchangeFilterFunctionITests {
 	private MockHttpServletRequest request;
 	private MockHttpServletResponse response;
 
-	@BeforeClass
-	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.
-		BlockHound.builder()
-				.allowBlockingCallsInside(Class.class.getName(), "getPackage")
-				.install();
-	}
-
 	@Before
 	public void setUp() throws Exception {
 		this.clientRegistrationRepository = mock(ClientRegistrationRepository.class);