Bump dep openssh-mux-client to v0.15.0

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

Author: NobodyXu

Cargo.toml

@@ -47,7 +47,7 @@ io-lifetimes = "0.6"
 once_cell = "1.10.0"
 dirs = "4.0.0"
 
-openssh-mux-client = { version = "0.14.4", optional = true }
+openssh-mux-client = { version = "0.15.0", optional = true }
 
 [dev-dependencies]
 lazy_static = "1.4.0"