Consider removing the "commitFile" logic from CASQueueFile

Nobody has claimed this yet.

`CASQueueFile` writes its header to a [a temporary `commitFile`](https://github.com/linkedin/cassette/blob/fc545125a481dcafa9cde96ed151d811d5855d93/Cassette/CASQueueFile.m#L564) with comments suggesting it should try and recover from failure when updating the metadata header.

This logic [does not exist in the Java implementation of `tape`](https://github.com/square/tape/blob/445cd3fd0a7b3ec48c9ea3e0e86663fe6d3735d8/tape/src/main/java/com/squareup/tape2/QueueFile.java#L265).

Worse yet, the Objective-C implementation does not actually recover from failure; it [silently discards the queue file entirely](https://github.com/linkedin/cassette/blob/fc545125a481dcafa9cde96ed151d811d5855d93/Cassette/CASQueueFile.m#L78) and pretends like the queue was empty.

Probably this logic should just be deleted. Either we assume the OS writes the header atomically (in which case we don't need the temporary `commitFile`), or we need to write the entire queue (header *and* data) to a temporary file, then rename the temporary file over the real file.

Read Cassette/CASQueueFile.m at the commitFile logic around line 564 and the failure handling around line 78, then compare the referenced Java QueueFile implementation. Verify what happens when updating the metadata header fails and whether the queue is discarded; done means the commitFile behavior is removed or replaced with a clearly tested recovery approach.

Written by the indexing model from the issue text.