Use __construct for the widget class instead

[kminh]

Resolves:

https://wordpress.org/support/topic/bwp-using-deprecated-constructor?replies=2#post-7823858
https://wordpress.org/support/topic/wp_widget-needs-updated-to-_construct?replies=2#post-8186499
https://wordpress.org/support/topic/the-called-constructor-method-for-wp_widget-in-bwp_rc_widget-is-deprecated/