Fix Cargo.toml whitespace.

Author: nnethercote

compiler/rustc_driver_impl/Cargo.toml

@@ -42,7 +42,7 @@ rustc_privacy = { path = "../rustc_privacy" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc_resolve = { path = "../rustc_resolve" }
 rustc_session = { path = "../rustc_session" }
-rustc_smir ={ path = "../rustc_smir" }
+rustc_smir = { path = "../rustc_smir" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }