Bump bdk_wallet version to 1.0.0-beta.6 #1409

Job	Run time
Check no_std	11s
Build and test (stable, true, --no-default-features --features miniscript/no-std)	1m 22s
Build and test (stable, true, --all-features)	4m 1s
Rust fmt	7s
Check WASM	32s
Build & Test Examples (example_cli)	20s
Build and test (1.63.0, --no-default-features --features miniscript/no-std)	2m 15s
Build & Test Examples (example_bitcoind_rpc_polling)	31s
prepare	2s
Build and test (1.63.0, --all-features)	4m 58s
Build & Test Examples (example_electrum)	43s
Build & Test Examples (example_esplora)	53s
Build & Test Examples (example_wallet_electrum)	46s
Build & Test Examples (example_wallet_esplora_async)	59s
Build & Test Examples (example_wallet_esplora_blocking)	1m 17s
Build & Test Examples (example_wallet_rpc)	43s
clippy_check	35s
	20m 15s

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