Fixes trueValue value evaluation on BaseSessionDriver constructor

[TiagoTeixeira85]

Problem Statement

The constructor for BaseSessionDriver class evaluates the following code $isPHP7 && self::$trueValue = true && self::$falseValue = false; to false for variable self::$trueValue.
So when Files class calls the open() method, the return value for the function self::true() returns false, resulting on the session file and cookie not being created.

Tested on PHP 7.4.30 using the Files driver using version 1.1-stable

Fix solution
Changing the aforementioned evaluation code to $isPHP7 && (self::$trueValue = true) && ((self::$falseValue = false) === false); fixes the issue.