Cargo install to point at v0.5.0 branch

Co-authored-by: Vaughn Dice <vaughn.dice@fermyon.com>
Signed-off-by: Mikkel Mork Hegnhoj <mikkel@fermyon.com>

Author: mikkelhegn

docs/content/quickstart.md

@@ -49,7 +49,7 @@ $ ./target/release/spin --help
 If you have [`cargo`](https://doc.rust-lang.org/cargo/getting-started/installation.html), you can clone the repo and install it to your path:
 
 ```console
-$ git clone https://github.com/fermyon/spin -b v0.4.0
+$ git clone https://github.com/fermyon/spin -b v0.5.0
 $ cd spin
 $ rustup target add wasm32-wasi
 $ cargo install --locked --path .