build(pom): upgrade modelVersion to 4.1.0 for Maven 4

Author: loong10k

pom.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
+<project xmlns="http://maven.apache.org/POM/4.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.1.0 http://maven.apache.org/xsd/maven-4.1.0.xsd">
+    <modelVersion>4.1.0</modelVersion>
     <groupId>io.github.easy4j</groupId>
     <artifactId>codex-java-sdk</artifactId>
     <name>${project.groupId}:${project.artifactId}</name>