Replace dynamic error message with static "Access Denied"

Closes gh-16514

Signed-off-by: Daeho Kwon <trewq231@naver.com>

test/src/test/java/org/springframework/security/test/web/reactive/server/SecurityMockServerConfigurersTests.java

@@ -136,7 +136,7 @@ public class SecurityMockServerConfigurersTests extends AbstractMockServerConfig
 			.expectStatus()
 			.isEqualTo(HttpStatus.FORBIDDEN)
 			.expectBody()
-			.consumeWith((b) -> assertThat(new String(b.getResponseBody())).contains("CSRF"));
+			.consumeWith((b) -> assertThat(new String(b.getResponseBody())).contains("Access Denied"));
 		this.client.mutateWith(SecurityMockServerConfigurers.csrf()).post().exchange().expectStatus().isOk();
 	}