Reland "[webgpu-headers] Removes define for signalValue."

This is a reland of commit 79cd63939a7cb9d56cd5ebfc2af6d7e225cd102d

Original change's description:
> [webgpu-headers] Removes define for signalValue.
>
> See issue: github.com/webgpu-native/webgpu-headers/issues/130
>
> Change-Id: I8e37e489f864fe72a822d9ad0c3d42c780023997
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/155980
> Kokoro: Kokoro <noreply+kokoro@google.com>
> Commit-Queue: Loko Kung <lokokung@google.com>
> Reviewed-by: Austin Eng <enga@chromium.org>

Change-Id: I8e70d9d04079f60aeec72d4a62d08b34a8d6e2df
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/155991
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>
diff --git a/generator/templates/api.h b/generator/templates/api.h
index 0232d46..894df1f 100644
--- a/generator/templates/api.h
+++ b/generator/templates/api.h
@@ -67,8 +67,6 @@
 #define {{API}}_NULLABLE
 #endif
 
-#define WGPU_BREAKING_WORK_DONE_SIGNAL_VALUE_CHANGE
-
 #include <stdint.h>
 #include <stddef.h>