fix(cache): use NewVerifier instead of deprecated NewSignedEntityVerifier

Replace deprecated verify.NewSignedEntityVerifier with verify.NewVerifier
to fix staticcheck warning SA1019.

The API is identical, just renamed:
- Old: verify.NewSignedEntityVerifier(trustedRoot, options...)
- New: verify.NewVerifier(trustedRoot, options...)

Changes:
- pkg/leeway/cache/slsa/verifier.go: Use verify.NewVerifier

Testing:
- All tests pass
- staticcheck passes with no warnings
- Functionality unchanged (same API, just renamed)

Fixes: SA1019: verify.NewSignedEntityVerifier is deprecated

Co-authored-by: Ona <no-reply@ona.com>

Author: leodido

pkg/leeway/cache/slsa/verifier.go

@@ -78,7 +78,7 @@ func (v *Verifier) VerifyArtifact(ctx context.Context, artifactPath, attestation
 	// Step 3: Create a verifier with transparency log verification
 	// WithTransparencyLog(1) means "require at least 1 transparency log entry"
 	// WithIntegratedTimestamps(1) means "require at least 1 integrated timestamp"
-	verifier, err := verify.NewSignedEntityVerifier(
+	verifier, err := verify.NewVerifier(
 		trustedRoot,
 		verify.WithTransparencyLog(1),
 		verify.WithIntegratedTimestamps(1),