Remove creation of new index when reindexing

[di]

This PR removes the new_index.create() call from the reindexing command. I think the explicit call to create a new index is unnecessary, because elasticsearch will automatically create an index if it has not been created before.

Furthermore, it is causing problems when reindexing in production:

• Prior to Optimize reindex #1471, this line was producing connection timeout errors nearly every time it was called;
• Since Optimize reindex #1471, the call can return before timing out, which produces a index_already_exists_exception instead (but still occasionally times out).

The latter issue leads me to believe that this due to a race condition with the automatic index creation -- since our "temporary" index is given a randomly-generated name every time, I don't see any other way that the index could already exist.

I can't reproduce either exception in local development. However, I have verified that reindexing still creates a new index and runs as expected without this line.

[di]

@dstufft, are you able to take a look at this? As noticed in #1489, the search index is getting somewhat stale due to this issue.