Upgrade to AssertJ 3.26.0

See https://github.com/assertj/assertj/issues/3322

framework-platform/framework-platform.gradle

@@ -15,7 +15,7 @@ dependencies {
 	api(platform("io.rsocket:rsocket-bom:1.1.3"))
 	api(platform("org.apache.groovy:groovy-bom:4.0.21"))
 	api(platform("org.apache.logging.log4j:log4j-bom:2.21.1"))
-	api(platform("org.assertj:assertj-bom:3.25.3"))
+	api(platform("org.assertj:assertj-bom:3.26.0"))
 	api(platform("org.eclipse.jetty:jetty-bom:12.0.9"))
 	api(platform("org.eclipse.jetty.ee10:jetty-ee10-bom:12.0.9"))
 	api(platform("org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.7.3"))

spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java

@@ -21,9 +21,7 @@ import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 
-import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.Test;
 import org.yaml.snakeyaml.composer.ComposerException;
 import org.yaml.snakeyaml.parser.ParserException;
@@ -34,6 +32,7 @@ import org.springframework.core.io.ByteArrayResource;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.entry;
+import static org.assertj.core.api.InstanceOfAssertFactories.set;
 
 /**
  * Tests for {@link YamlProcessor}.
@@ -142,13 +141,11 @@ class YamlProcessorTests {
 	}
 
 	@Test
-	@SuppressWarnings("unchecked")
 	void standardTypesSupportedByDefault() {
 		setYaml("value: !!set\n  ? first\n  ? second");
 		this.processor.process((properties, map) -> {
 			assertThat(properties).containsExactly(entry("value[0]", "first"), entry("value[1]", "second"));
-			assertThat(map.get("value")).asInstanceOf(InstanceOfAssertFactories.type(Set.class))
-					.satisfies(set -> assertThat(set).containsExactly("first", "second"));
+			assertThat(map.get("value")).asInstanceOf(set(String.class)).containsExactly("first", "second");
 		});
 	}
 

spring-web/src/test/java/org/springframework/http/server/reactive/HeadersAdaptersTests.java

@@ -28,7 +28,6 @@ import java.util.stream.Stream;
 import io.netty.handler.codec.http.DefaultHttpHeaders;
 import io.undertow.util.HeaderMap;
 import org.apache.tomcat.util.http.MimeHeaders;
-import org.assertj.core.api.StringAssert;
 import org.eclipse.jetty.http.HttpFields;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
@@ -90,7 +89,7 @@ class HeadersAdaptersTests {
 		headers.add("TestHeader", "first");
 		headers.add("TestHeader", "second");
 		assertThat(headers.getFirst("TestHeader")).isEqualTo("first");
-		assertThat(headers.get("TestHeader"), StringAssert.class).element(0).isEqualTo("first");
+		assertThat(headers.get("TestHeader")).first().isEqualTo("first");
 	}
 
 	@ParameterizedHeadersTest