ci: drop redundant setup-bun step that stalls Gitea runner

bun is already baked into the jellytau-builder image (Dockerfile.builder),
so oven-sh/setup-bun@v1 was redundant. Fetching that GitHub-hosted action
from the self-hosted Gitea runner hangs the job before any steps run.
Removed from traceability-check, traceability, and publish-docs workflows;
build-and-test and build-release never used it and never stalled.

.gitea/workflows/traceability.yml

@@ -23,11 +23,8 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Setup Bun
-        uses: oven-sh/setup-bun@v1
-        with:
-          bun-version: latest
-
+      # bun is baked into jellytau-builder (see Dockerfile.builder); no setup-bun
+      # action needed — fetching it stalls on this Gitea runner.
       - name: Install dependencies
         run: bun install