wp.sanitize.stripTags should iterate instead of using recursion

[jrchamp]

The changes to wp-sanitize.js seemed wasteful and like it produced dead code in the final return.

​https://github.com/WordPress/WordPress/commit/90d9bdc54c82229b3aa5a6e60d775f14b1f9a9dc#diff-9bedaa5d6abc6cb127b2f496bb2f7835

When I got into it to fix the dead code, I also felt a way about the recursion, because stack and memory exhaustion are two other potential issues. So this way should *at most* be one function call and only duplicate memory instead of being O(n*memory).

​https://github.com/WordPress/WordPress/commit/d9b128f50546a65c9cf0944ee61237e35ff269c0

This is probably a drive-by commit and for that I apologize. I hope it's more useful than not, but your mileage may vary. Thank you for making WordPress.