[scripts] remove cargo-lipo from rustup setup

Summary: we don't need this anymore since we're building a target-specific native_rust_library now

Test Plan: uninstalled cargo-lipo and successfully built the iOS app. confirmed that cargo-lipo still wasn't installed on my machine after build

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek, wyilio

Differential Revision: https://phab.comm.dev/D9635

scripts/ensure_rustup_setup.sh

@@ -19,7 +19,3 @@ fi
 
 ensure_target aarch64-apple-ios
 ensure_target x86_64-apple-ios
-
-if ! command -v cargo-lipo > /dev/null; then
-  cargo install cargo-lipo
-fi