Deleted 4 old and low rated notes

Following were the 4 notes with a rating less than -5 and
are older than 1 year.

These notes represented 0.0% of the 16580 total user notes,
and have now been removed.

Rating | Note
-------+---------------------------------------------------------
   -7  | https://php.net/manual/en/reserved.classes.php#73316
   -6  | https://php.net/manual/en/function.array-filter.php#127216
   -6  | https://php.net/manual/en/function.openssl-csr-sign.php#89083
   -6  | https://php.net/manual/en/ref.classobj.php#50578