jetbrains.rust-rover: fix darwin install (#258814)

* jetbrains.rust-rover: fix darwin install

JetBrains doesn't guarantee that the macOS app will be called
`${product}.app` so I modified the installPhase to copy *.app instead
of ${product}.app, which fails on file does not exist for Rust Rover,
which is `RustRover 2023.2 EAP.app`

I've tested with some other JetBrains apps on darwin aarch64 and they
continue to build as expected.

pkgs/applications/editors/jetbrains/darwin.nix

···
     runHook preInstall
     APP_DIR="$out/Applications/${product}.app"
     mkdir -p "$APP_DIR"
-    cp -Tr "${product}.app" "$APP_DIR"
+    cp -Tr *.app "$APP_DIR"
     mkdir -p "$out/bin"
     cat << EOF > "$out/bin/${loname}"
     open -na '$APP_DIR' --args "\$@"