CI: remove slowed-network tests

- remove these tests as they are currently not reliable in our CI
  setups.

curl handles the test cases, but CI sometimes fails on these due to
additional conditions. Rather than mix them in, an additional CI job
will be added in the future that is specific to them.

Closes https://github.com/curl/curl/pull/12075

.github/workflows/ngtcp2-linux.yml

@@ -268,12 +268,3 @@ jobs:
       env:
         TFLAGS: "${{ matrix.build.tflags }}"
         CURL_CI: github
-
-    - run: pytest -v tests
-      name: 'run pytest with slowed network'
-      env:
-        # 33% of sends are EAGAINed
-        CURL_DBG_SOCK_WBLOCK: 33
-        # only 80% of data > 10 bytes is send
-        CURL_DBG_SOCK_WPARTIAL: 80
-        CURL_CI: github