test: move test file to sequential/ due to timing issues
Moving test-http-server-request-timeouts-mixed from tests/parallel to tests/sequential
The flaky test is reproducible when we run tools/test.py -j96 --repeat=1024 test/parallel/test-http-server-request-timeouts-mixed.js. I tried tuning the timeouts at which the values are asserted, but they still seem to fail because of timing issues when the system is burdened.
As a workaround, I have moved the test to run sequentially(verified it with tools/test.py -j96 --repeat=128 test/sequential/test-http-server-request-timeouts-mixed.js)