Remove unit test that triggers frequent intermittent failure.

[jdm]

This works around #26895 by removing the test that triggers it. The underlying cause of the failure isn't clear, but it's something to do with the hyper server and doesn't appear to impact the way that Servo's HTTP stack functions. The unit test itself is testing one particular property of the way CORS requests are made with HEAD requests, and that's not a property that is critical functionality if we stop testing it.

[highfive]

Heads up! This PR modifies the following files:

• @KiChjang: components/net/tests/http_loader.rs

[jdm]

r? @asajeffrey

[SimonSapin]

error: unused imports: `AccessControlAllowOrigin`, `Origin`
  --> components/net/tests/http_loader.rs:19:5
   |
19 |     AccessControlAllowOrigin, Authorization, ContentLength, Date, HeaderMapExt, Host, Origin,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^                                                          ^^^^^^
   |
   = note: `-D unused-imports` implied by `-D warnings`
error: unused import: `RequestMode`
  --> components/net/tests/http_loader.rs:37:34
   |
37 |     RequestBody, RequestBuilder, RequestMode,
   |                                  ^^^^^^^^^^^

[CYBAI]

Missing one 👀

error: unused import: `Origin`
  --> components/net/tests/http_loader.rs:19:61
   |
19 |     Authorization, ContentLength, Date, HeaderMapExt, Host, Origin, StrictTransportSecurity,
   |                                                             ^^^^^^
   |
   = note: `-D unused-imports` implied by `-D warnings`

[nox]

@bors-servo r+

[bors-servo]

📌 Commit 7775833 has been approved by nox

[bors-servo]

⌛ Testing commit 7775833 with merge 5a8023d...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: nox
Pushing 5a8023d to master...