git: openjdk/loom: fibers: decrease number of threads in SuspendResume* tests from 30 to 20 in native agent

[duke]

Changeset: 8838e0a5
Author:    Serguei Spitsyn <serguei.spitsyn at oracle.com>
Date:      2021-08-20 04:53:12 +0000
URL:       https://git.openjdk.java.net/loom/commit/8838e0a5efc922f1044c07da4721c127195ae9d8

decrease number of threads in SuspendResume* tests from 30 to 20 in native agent

! test/hotspot/jtreg/serviceability/jvmti/vthread/SuspendResume1/libSuspendResume1.cpp
! test/hotspot/jtreg/serviceability/jvmti/vthread/SuspendResume2/libSuspendResume2.cpp