Small tweak to search bar in help center

[hedgefield]

I'm working on making the search bars more accessible and consistent, and the one in the KB tab of the Help Center is so close.

All it needs is:

• Remove the search icon
• Extend the search bar towards the left so it fills up the empty space left by removing the icon
• Change the label to Search the Yoast Knowledge Base for answers to your questions:
• Change the placeholder to Type here to search...