test: move test to sequential for reliability
test-https-set-timeout-server fails under load. Move it to sequential so it is not competing with other tests.
Fixes: https://github.com/nodejs/node/issues/10130
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines
Affected core subsystem(s)
test https freebsd