temporary disable "neon" feature of chacha20

ref #19
ref RustCrypto/stream-ciphers#312

Author: zonyitoo

Cargo.toml

@@ -37,7 +37,7 @@ md-5 = { version = "0.10" }
 hkdf = { version = "0.12", optional = true }
 sha1 = { version = "0.10", optional = true }
 blake3 = { version = "1.3", optional = true }
-chacha20 = { version = "0.9", features = ["neon"], optional = true }
+chacha20 = { version = "0.9", features = [], optional = true }
 aes = { version = "0.8", optional = true }
 ctr = { version = "0.9", optional = true }
 bytes = { version = "1.3", optional = true }