adds comment on exception with simple name NotFound

[skip ci]

Author: mkristian

src/main/java/org/jruby/ext/openssl/x509store/Store.java

@@ -374,6 +374,8 @@ public int setDefaultPaths(Ruby runtime) throws Exception {
             // set_default_paths ignores FileNotFound
         }
         catch (IOException e) {
+            // this is for older jrubies as they do not have a
+            // org.jruby.util.ResourceException.NotFound
             if (!e.getClass().getSimpleName().equals("NotFound")) {
                 throw e;
             }