kernel-test.yml: decrease VMTEST_MEMORY to 5G (#425)

This helps with memory pressure on s390x runners, when the load is high.

Author: theihor

.github/workflows/kernel-test.yml

@@ -76,7 +76,7 @@ jobs:
           KERNEL_TEST: ${{ inputs.test }}
           SELFTESTS_BPF: ${{ github.workspace }}/selftests/bpf
           VMTEST_CONFIGS: ${{ github.workspace }}/ci/vmtest/configs
-          VMTEST_MEMORY: 6G
+          VMTEST_MEMORY: 5G
           VMTEST_NUM_CPUS: 4
           TEST_PROGS_TRAFFIC_MONITOR: ${{ inputs.arch == 'x86_64' && 'true' || '' }}
           TEST_PROGS_WATCHDOG_TIMEOUT: 600