The Bug:

Two mysterious white pixels can be seen in the upper left corner of the recipe book icon.

Steps to Reproduce:

• Switch into survival mode.
• Open up your inventory.
• Look at the recipe book icon.
  →  Notice how there are two mysterious white pixels in the upper left corner of the icon.

Information:

This did not happen in 1.16.5 or 21w08b. Could be intentional.