Bug 1499834 [wpt PR 13579] - Added 304 CSP test and removed "content-…

…*" prefix from headers to ignore on 304, a=testonly

Automatic update from web-platform-testsAdded 304 CSP test and removed "content-*" prefix from headers to ignore on 304

Also updated kNonUpdatedHeaders with more headers from the
nsHttpResponseHead file

Spec: https://fetch.spec.whatwg.org/#concept-http-network-or-cache-fetch
Spec issue: w3c/webappsec-csp#161

While the spec does not give any list of content headers that should be ignored
on a 304 request, some of them are directly dependent on the resource body and
as such should not be updated (for example `content-length` cannot be different
since the content remains identical).

The exact list of ignored headers is identical to the one that firefox uses.

Bug: 174301
Change-Id: I8aab863b1f2733d051609e121539ad6acad36c6b
Reviewed-on: https://chromium-review.googlesource.com/c/1286427
Commit-Queue: Andy Paicu <andypaicuchromium.org>
Reviewed-by: Mike West <mkwstchromium.org>
Reviewed-by: Matt Menke <mmenkechromium.org>
Cr-Commit-Position: refs/heads/master{#602001}

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wpt-commits: 1b09004d92653856ca896d0f267d42bfda788434
wpt-pr: 13579

UltraBlame original commit: c94869a31c0e382016b7c0c41c931560ebcfd9e6