Feat: Improve FlexSlider initialization and element selection in JavaScript

• Updated the initialization of FlexSlider by using a regular function instead of an arrow function in the flexslider.load.js and flexslider.load.min.js files.
• Updated the element selection in the flexslider.load.js and flexslider.load.min.js files to use $(this) instead of $(once(...)) and $(_this) respectively.

Changes:

• assets/js/flexslider.load.js: Improved FlexSlider initialization and element selection.
• dist/js/flexslider.load.js: Improved FlexSlider initialization and element selection.
• dist/js/flexslider.load.min.js: Improved FlexSlider initialization and element selection.