util: remove unreachable inspect code

Convert invariant from if statement to an assertion. The condition is
believed to be impossible to trigger.

PR-URL: #37941
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/util/inspect.js

@@ -1438,9 +1438,7 @@ function formatNamespaceObject(keys, ctx, value, recurseTimes) {
       output[i] = formatProperty(ctx, value, recurseTimes, keys[i],
                                  kObjectType);
     } catch (err) {
-      if (!(isNativeError(err) && err.name === 'ReferenceError')) {
-        throw err;
-      }
+      assert(isNativeError(err) && err.name === 'ReferenceError');
       // Use the existing functionality. This makes sure the indentation and
       // line breaks are always correct. Otherwise it is very difficult to keep
       // this aligned, even though this is a hacky way of dealing with this.