chore!: Upgrade to SLF4J 2.0 (#14916)

Spring Boot 3 RC1 and newer depend on SLF4J 2

Author: Artur-

flow-server/src/test/java/com/vaadin/flow/server/startup/VaadinAppShellInitializerTest.java

@@ -28,7 +28,7 @@
 import org.slf4j.ILoggerFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.slf4j.impl.SimpleLoggerFactory;
+import org.slf4j.simple.SimpleLoggerFactory;
 
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.PushConfiguration;

pom.xml

@@ -89,7 +89,7 @@
         <spring.security.oauth2.authorization.server.version>1.0.0-M2</spring.security.oauth2.authorization.server.version>
         <gwt.version>2.9.0</gwt.version>
         <hibernate.validator.version>7.0.2.Final</hibernate.validator.version>
-        <slf4j.version>1.7.36</slf4j.version>
+        <slf4j.version>2.0.3</slf4j.version>
         <polymer.version>2.6.1</polymer.version>
         <jackson.version>2.13.4</jackson.version>
         <jackson.databind.version>2.13.4.2</jackson.databind.version>