README: fix instructions for installing target arches

The literal `\`s were not formatted well

Author: richvdh

README.md

@@ -43,11 +43,7 @@ Other useful flags:
 * the Rust toolchain
 * cargo-ndk `cargo install cargo-ndk`
 * protoc `brew install protobuf` or downloading [here](https://github.com/protocolbuffers/protobuf/releases)
-* android targets (e.g. `rustup target add \
-  aarch64-linux-android \
-  armv7-linux-androideabi \
-  x86_64-linux-android \
-  i686-linux-android`)
+* android targets (e.g. `rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android i686-linux-android`)
 
 
 ## License