The blocks in the inventory are not lit enough on their top

The bug

The blocks in the inventory are not lit enough on their top, in comparison with 1.14.4.
This can sometimes lead to confusion of blocks, especially in terms of colors (accessibility).

Examples

Here are (only) a few obvious examples:

• The grass block:
  1.14.4: 1.15:

• The leaves:
  1.14.4: 1.15:

• The banners:
  1.14.4: 1.15: