ci: update minimum rust version to 1.70 #4233

Job	Run time
bdk_test	3m 6s
sqlx_test	3m 54s
build (x86_64-unknown-linux-gnu, ubuntu-latest)	5m 30s
docker_tests (happy_path)	4m 38s
build (armv7-unknown-linux-gnueabihf, ubuntu-latest)	6m 15s
static_analysis	1m 4s
docker_tests (happy_path_restart_bob_after_xmr_locked)	4m 40s
test (ubuntu-latest)	9m 39s
build (x86_64-apple-darwin, macos-latest)	3h 24m 30s
docker_tests (happy_path_restart_bob_before_xmr_locked)	4m 35s
test (macos-latest)	12m 33s
build (x86_64-pc-windows-msvc, windows-latest)	7m 15s
docker_tests (happy_path_restart_alice_after_xmr_locked)	4m 32s
docker_tests (alice_and_bob_refund_using_cancel_and_refund_command)	4m 23s
docker_tests (alice_and_bob_refund_using_cancel_then_refund_command)	4m 26s
docker_tests (alice_and_bob_refund_using_cancel_and_refund_command_timelock_not_expired)	4m 25s
docker_tests (punish)	4m 46s
docker_tests (alice_punishes_after_restart_bob_dead)	4m 44s
docker_tests (alice_manually_punishes_after_bob_dead)	4m 46s
docker_tests (alice_refunds_after_restart_bob_refunded)	4m 31s
docker_tests (ensure_same_swap_id)	4m 17s
docker_tests (concurrent_bobs_before_xmr_lock_proof_sent)	7m 27s
docker_tests (alice_manually_redeems_after_enc_sig_learned)	4m 40s
	5h 20m 36s

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