cleanup db_now() phpdoc

db_now() returns a Unix timestamp, not a DATETIME-formatted string as
currently described in the DocBlock. This updates the function
description.

Fixes #21725

Signed-off-by: Damien Regad <dregad@mantisbt.org>

core/database_api.php

@@ -838,9 +838,8 @@ function db_prepare_bool( $p_bool ) {
 }
 
 /**
- * return current timestamp for DB
- * @todo add param bool $p_gmt whether to use GMT or current timezone (default false)
- * @return string Formatted Date for DB insertion e.g. 1970-01-01 00:00:00 ready for database insertion
+ * return current time as Unix timestamp
+ * @return integer Unix timestamp of the current date and time
  */
 function db_now() {
 	return time();
@@ -1289,4 +1288,4 @@ function db_mysql_fix_utf8( $p_string ) {
  */
 function db_empty_result() {
 	return new ADORecordSet_empty();
-}
+}