[fetch] Algorithm for exluded headers in CORS filtered responses is hard to parse (#202)

```
A CORS filtered response is a filtered response whose type is "cors", header list excludes all headers in internal response's header list, except those whose name is either one of `Cache-Control`, `Content-Language`, `Content-Type`, `Expires`, `Last-Modified`, and `Pragma`, and except those whose name is both not a forbidden response-header name and one of the values resulting from parsing `Access-Control-Expose-Headers` in internal response's header list. 
```
I believe this translates to "everything is excluded, unless: (one of special list) or ((not forbidden) and (in A-C-E-H))", but I've had to read it carefully a number of times to come to that understanding.

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/202