[keys] limit version of zeroize to support rust 1.47+

Author: notmandatory

Cargo.toml

@@ -31,6 +31,7 @@ cc = { version = ">=1.0.64", optional = true }
 socks = { version = "0.3", optional = true }
 lazy_static = { version = "1.4", optional = true }
 tiny-bip39 = { version = "^0.8", optional = true }
+zeroize = { version = "<1.4.0", optional = true }
 bitcoinconsensus = { version = "0.19.0-3", optional = true }
 
 # Needed by bdk_blockchain_tests macro
@@ -56,7 +57,7 @@ compact_filters = ["rocksdb", "socks", "lazy_static", "cc"]
 key-value-db = ["sled"]
 async-interface = ["async-trait"]
 all-keys = ["keys-bip39"]
-keys-bip39 = ["tiny-bip39"]
+keys-bip39 = ["tiny-bip39", "zeroize"]
 rpc = ["bitcoincore-rpc"]