docs: use stable Rust toolchain for installation
We don't need the nightly toolchain anymore since (thanks,
@@ -135,10 +135,7 @@ $ export PKG_CONFIG_PATH="/opt/homebrew/opt/openssl@3/lib/pkgconfig"
Now run this (regardless of platform):
```shell script
-# We need the "nightly" Rust toolchain. This command installs that without
-# changing your default.
-$ rustup install nightly
-$ cargo +nightly install --git https://github.com/martinvonz/jj.git
+$ cargo install --git https://github.com/martinvonz/jj.git
```
To set up command-line completion, source the output of
