Simplify `cargo deb` usage

INSTALL.md

@@ -251,7 +251,7 @@ Using `cargo deb`, you can create and install a deb file.
 
 ```sh
 cargo install cargo-deb
-cargo deb --install --manifest-path alacritty/Cargo.toml
+cargo deb --install -p alacritty
 ```
 
 To choose a default terminal app, use Debian's `update-alternatives`.

ci/before_deploy.sh

@@ -60,7 +60,7 @@ function docker_deb {
     archname=$2
 
     docker run -v "$(pwd):/source" "undeadleech/${image}" sh -c \
-        "cd /source && /root/.cargo/bin/cargo deb --no-build --manifest-path alacritty/Cargo.toml \
+        "cd /source && /root/.cargo/bin/cargo deb --no-build -p alacritty \
         --output ./target/deploy/${name}-${archname}.deb"
 }