Revert Cargo.toml azure_core version back from 0.2.1 to 0.2

Author: johnbatty

sdk/security_keyvault/Cargo.toml

@@ -21,7 +21,7 @@ serde_json = "1.0"
 url = "2.2"
 serde = { version = "1.0", features = ["derive"] }
 getset = "0.1"
-azure_core = { path = "../core", version = "0.2.1" }
+azure_core = { path = "../core", version = "0.2" }
 
 [dev-dependencies]
 oauth2 = "4.0.0"