build-style cargo: move cargo config from wrksrc to home

since cargo 0.31.0 ${wrksrc}/.cargo/config is ignored for cargo install
fixes: https://github.com/void-linux/void-packages/issues/4328

common/environment/build-style/cargo.sh

@@ -4,7 +4,4 @@ if [ "$CROSS_BUILD" ]; then
 	makedepends+=" rust-std"
 fi
 
-# Use the config we set in do_configure
-export CARGO_HOME="$wrksrc/.cargo"
-
 export PKG_CONFIG_ALLOW_CROSS=1