Update types.build.provisioners.go

if pause_before is invalid, that's an error

hcl2template/types.build.provisioners.go

@@ -120,6 +120,7 @@ func (p *Parser) decodeProvisioner(block *hcl.Block, cfg *PackerConfig) (*Provis
 		if err != nil {
 			return nil, append(diags, &hcl.Diagnostic{
 				Summary:  "Failed to parse pause_before duration",
+				Severity: hcl.DiagError,
 				Detail:   err.Error(),
 			})
 		}