Update reference to cargo's `--offline` feature

docs/src/commands/build.md

@@ -130,10 +130,10 @@ wasm-pack build examples/js-hello-world --mode no-install
 The `build` command can pass extra options straight to `cargo build` even if they are not
 supported in wasm-pack. To use them you should add standalone `--` argument at the very
 end of your command, and all the arguments you want to pass to cargo should go after.
-For example to build previous example using unstable cargo offline feature:
+For example, to build the previous example using cargo's offline feature:
 
 ```
-wasm-pack build examples/js-hello-world --mode no-install -- -Z offline
+wasm-pack build examples/js-hello-world --mode no-install -- --offline
 ```
 
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