fix(materials): remove assertion on deprecated Artifact.Id field

The Id field is deprecated in crafting_state.proto (kept only for
server-side compatibility). Remove the test assertion to fix the
SA1019 staticcheck lint failure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Vibhav Bobade <vibhav.bobde@gmail.com>

Author: waveywaves

pkg/attestation/crafter/materials/spdxjson_test.go

@@ -215,7 +215,6 @@ func TestSPDXJSONCraft(t *testing.T) {
 			require.NotNil(t, sbomArtifact)
 			assert.Equal(tc.wantDigest, sbomArtifact.Artifact.Digest)
 			assert.Equal(tc.wantFilename, sbomArtifact.Artifact.Name)
-			assert.Equal("test", sbomArtifact.Artifact.Id)
 
 			// Validate main component extraction
 			if tc.wantNoMainComponent {