Don't convert SchemeHostPort in {Get,Set}SupportsSpdy()

These two methods are used from three places. (1)
HttpStreamFactory::Job, (2) HttpStreamPool::AttemptManager, and (3)
HttpServerProperties.

(1) and (2) ensures that `server` argument has either http:// or
https://. (3) didn't check the scheme. This CL modifies to call
GetSupportsSpdy() only when the scheme is http(s)://.

Now we don't need to convert the argument using
NormalizeSchemeHostPort() in {Get,Set}SupportsSpdy(). Change DCHECKs to
CHECKs for scheme checks. Remove
HttpServerPropertiesTest.SetSupportsSpdyWebSockets since the test
violates the precondition.

This is a preparation for reducing aborted attempts in the HEv3 code
path.

Bug: 384759483
Change-Id: I3b7710ced8692a7b3edbb1d0c966dd5102b129c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6247897
Reviewed-by: mmenke <mmenke@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1420889}