docs(parser): add regeneration warning to SimpleCharStream header

The file is maintained by hand on top of the JavaCC template and carries
the in-buffer rewrite of a leading # in BeginToken(), which
Feature.allowHashLineComments depends on. Per review on #2508.

Author: fudianchn

src/main/java/net/sf/jsqlparser/parser/SimpleCharStream.java

@@ -8,6 +8,12 @@
  * #L%
  */
 /* Generated By:JavaCC: Do not edit this line by hand. SimpleCharStream.java Version 8.0.0 */
+/*
+ * Warning: this file is maintained by hand on top of the JavaCC template. Among other manual
+ * adjustments it carries the in-buffer '#' rewrite in BeginToken(), which
+ * Feature.allowHashLineComments depends on. Never overwrite it with a freshly generated
+ * SimpleCharStream, that would silently drop the rewrite and break allowHashLineComments.
+ */
 package net.sf.jsqlparser.parser;
 
 import net.sf.jsqlparser.parser.feature.Feature;