ci: reduce target bitrate for UDP perf tests to 600Mbit/s (#10312)

To achieve a more stable CI, we need to reduce the target bitrate of the
UDP perf tests. Now that we no longer have GSO enabled in the tests, the
most we can achieve in CI is 600Mbit/s. Forcing more packets through the
tunnel results in all sorts of warnings which end up failing CI.

scripts/tests/perf/direct-udp-client2server.sh

@@ -7,7 +7,7 @@ source "./scripts/tests/lib.sh"
 docker compose exec --env RUST_LOG=info -it client /bin/sh -c 'iperf3 \
   --time 30 \
   --udp \
-  --bandwidth 1G \
+  --bandwidth 600M \
   --client 172.20.0.110 \
   --json' >>"${TEST_NAME}.json"
 

scripts/tests/perf/direct-udp-server2client.sh

@@ -8,7 +8,7 @@ docker compose exec --env RUST_LOG=info -it client /bin/sh -c 'iperf3 \
   --time 30 \
   --reverse \
   --udp \
-  --bandwidth 1G \
+  --bandwidth 600M \
   --client 172.20.0.110 \
   --json' >>"${TEST_NAME}.json"