fix(release): Remove duplicate SBOM upload in goreleaser config

The sboms: section already uploads CycloneDX and SPDX documents.
The extra_files: section was trying to upload them a second time,
causing "already_exists" 422 errors on the GitHub Release API.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pmclSF

.goreleaser.yaml

@@ -111,6 +111,3 @@ release:
   github:
     owner: pmclSF
     name: terrain
-  extra_files:
-    - glob: "dist/*.cdx.json"
-    - glob: "dist/*.spdx.json"