portable: do not use SYNTHETIC_ERRNO for sd_bus_error_set_errno()

The concept of synthetic errnos is about logging, which
is irrelevant irt bus error and we don't do any special
treatment in sd-bus for them, meaning the value propagated
would be spurious.

(cherry picked from commit 2f2058d)
(cherry picked from commit 018c7fb)
(cherry picked from commit 39c2b7f)
(cherry picked from commit 06be1bf)

Author: YHNdnzj

src/portable/portable.c

@@ -595,7 +595,7 @@ static int extract_image_and_extensions(
                 if (r < 0)
                         return r;
                 if (isempty(id))
-                        return sd_bus_error_set_errnof(error, SYNTHETIC_ERRNO(ESTALE), "Image %s os-release metadata lacks the ID field", name_or_path);
+                        return sd_bus_error_set_errnof(error, ESTALE, "Image %s os-release metadata lacks the ID field", name_or_path);
 
                 if (prefixes) {
                         valid_prefixes = strv_split(prefixes, WHITESPACE);
@@ -639,7 +639,7 @@ static int extract_image_and_extensions(
                 if (validate_sysext) {
                         r = extension_release_validate(ext->path, id, version_id, sysext_level, "portable", extension_release);
                         if (r == 0)
-                                return sd_bus_error_set_errnof(error, SYNTHETIC_ERRNO(ESTALE), "Image %s extension-release metadata does not match the root's", ext->path);
+                                return sd_bus_error_set_errnof(error, ESTALE, "Image %s extension-release metadata does not match the root's", ext->path);
                         if (r < 0)
                                 return sd_bus_error_set_errnof(error, r, "Failed to compare image %s extension-release metadata with the root's os-release: %m", ext->path);
                 }