webgpu.h: Remove WGPUProgrammableStageDescriptor alias

Bug: 379059434
Change-Id: I70c06b15dde1a0d1af0f3c317a32918d8db431f6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/219914
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Fr <beaufort.francois@gmail.com>

src/dawn/dawn.json

diff --git a/src/dawn/dawn.json b/src/dawn/dawn.json
index 0a6428b..85cacb8 100644
--- a/src/dawn/dawn.json
+++ b/src/dawn/dawn.json
@@ -2876,10 +2876,6 @@
             {"value": 4, "name": "mailbox"}
         ]
     },
-    "programmable stage descriptor": {
-        "category": "typedef",
-        "type": "compute state"
-    },
     "compute state": {
         "category": "structure",
         "extensible": "in",