Apply suggestions from code review

Co-authored-by: Clément Fournier <clement.fournier76@gmail.com>

pmd-java/etc/grammar/Java.jjt

@@ -481,7 +481,7 @@ public class JavaParser {
   }
 
   private void checkForNewStringSpaceEscape(String s) {
-    if (!(jdkVersion >= 15) && s.contains("\\s") && !s.contains("\\\\s")) {
+    if (jdkVersion < 15 && s.contains("\\s") && !s.contains("\\\\s")) {
       throwParseException("The escape sequence \"\\s\" is only supported with Java >= 15");
     }
   }

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTPermitsList.java

@@ -18,7 +18,7 @@ import net.sourceforge.pmd.annotation.Experimental;
  *
  * <pre class="grammar">
  *
- *  PermittedSubclasses ::= "permits" ClassOrInterfaceType
+ *  PermitsList ::= "permits" ClassOrInterfaceType
  *                ( "," ClassOrInterfaceType )*
  * </pre>
  */