docs: disable running example due to cross-realm issues

Author: kgryte

lib/node_modules/@stdlib/array/datespace/README.md

@@ -52,6 +52,10 @@ var arr = datespace( start, end, 6 );
 
 The `start` and `stop` times may be either [`Date`][mdn-date-object] objects, date strings, Unix timestamps, or JavaScript timestamps.
 
+<!-- FIXME: issue with executing in different realms and validating a Date object. -->
+
+<!-- run-disable -->
+
 ```javascript
 // JavaScript timestamps:
 var end = 1417503654973;