Improved visibility of #phpdebugbar-show-duplicates anchor tag in widget.js

[YazeedAlsaif]

In the widget.js file, I made the #phpdebugbar-show-duplicates anchor tag more visible by adding bold styles to it, indicating that it is clickable. I also updated the wording of the anchor tag to say "Show only duplicated queries" and "Show all queries" for clarity.

Please see the attached screenshot for reference:

Thank you for considering my contribution.

[erikn69]

Fixed on #1519