docs: changed "Done" to "DONE" in features.txt

Mesamatrix.net expects uppercase.

Acked-by: Timothy Arceri <tarceri@itsqueeze.com>
14 jobs for master in 17 minutes and 43 seconds (queued for 1 second)
Status Job ID Name Coverage
  Containers Build
passed #266612
debian

00:00:20

 
  Build+Test
passed #266614
meson-clang

00:17:20

passed #266620
meson-gallium-clover-llvm

00:01:49

passed #266621
meson-gallium-clover-llvm39

00:02:11

passed #266619
meson-gallium-drivers-other

00:04:09

passed #266618
meson-gallium-radeonsi

00:03:02

passed #266622
meson-gallium-st-other

00:01:38

passed #266613
meson-gallium-swr

00:01:07

passed #266617
meson-glvnd

00:10:41

passed #266616
meson-loader-classic-dri

00:03:25

passed #266615
meson-vulkan

00:09:06

passed #266624
scons-llvm

00:03:40

passed #266623
scons-nollvm

00:02:51

passed #266625
scons-swr

00:04:32