Fixup backing group computation time (#3170)

Fixes: https://github.com/paritytech/polkadot-sdk/issues/3165

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

polkadot/zombienet_tests/functional/0011-async-backing-6-seconds-rate.toml

@@ -0,0 +1,51 @@
+[settings]
+timeout = 1000
+
+[relaychain]
+default_image = "{{ZOMBIENET_INTEGRATION_TEST_IMAGE}}"
+chain = "rococo-local"
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config]
+  needed_approvals = 4
+  relay_vrf_modulo_samples = 6
+  scheduling_lookahead = 2
+  group_rotation_frequency = 4
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config.async_backing_params]
+  max_candidate_depth = 3
+  allowed_ancestry_len = 2
+
+[relaychain.default_resources]
+limits = { memory = "4G", cpu = "2" }
+requests = { memory = "2G", cpu = "1" }
+
+  [[relaychain.node_groups]]
+  name = "alice"
+  args = [ "-lparachain=debug" ]
+  count = 12
+
+[[parachains]]
+id = 2000
+addToGenesis = true
+genesis_state_generator = "undying-collator export-genesis-state --pov-size=100000 --pvf-complexity=1"
+
+  [parachains.collator]
+  name = "collator01"
+  image = "{{COL_IMAGE}}"
+  command = "undying-collator"
+  args = ["-lparachain=debug", "--pov-size=100000", "--pvf-complexity=1", "--parachain-id=2000"]
+
+[[parachains]]
+id = 2001
+cumulus_based = true
+
+  [parachains.collator]
+  name = "collator02"
+  image = "{{CUMULUS_IMAGE}}"
+  command = "polkadot-parachain"
+  args = ["-lparachain=debug"]
+
+[types.Header]
+number = "u64"
+parent_hash = "Hash"
+post_state = "Hash"