Fix PHPStan issue on ConditionInterface of \Drupal\Core\Database

Problem/Motivation

Currently PHPStan throws following error when following condition is given in select query

$items = $this->database->select($this->queueTable, 'q');
$items->condition('created', $this->requestTime - 86400, '<');

Error is given below:
parameter #2 $value of method Drupal\Core\Database\Query\ConditionInterface::condition() expects array|Drupal\Core\Database\Query\SelectInterface|string|null, int given.

Docblock of Drupal\Core\Database\Query\ConditionInterface's condition() method suggests that argument can be either string, null, array etc.
However, we can also pass integer etc. in the condition value.

Steps to reproduce

Add a database condition statement given in problem/motivation step.
Run phpstan check.

Proposed resolution

- Update proper docblock to allow integer value as well.

Remaining tasks

User interface changes

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A