Update Maven configuration to Java 21

Author: bhoffpauir

.classpath

@@ -26,7 +26,7 @@
 			<attribute name="optional" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-21">
 		<attributes>
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>

pom.xml

@@ -13,7 +13,7 @@
   <properties>
 	<exec.mainClass>com.bhoffpauir.blisp.interp.Main</exec.mainClass>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <maven.compiler.release>17</maven.compiler.release>
+    <maven.compiler.release>21</maven.compiler.release>
   </properties>
 
   <dependencies>