Remove unneeded dependency.

Author: nnethercote

Cargo.lock

@@ -4311,7 +4311,6 @@ dependencies = [
  "rustc_errors",
  "rustc_hir",
  "rustc_index",
- "rustc_macros",
  "rustc_middle",
  "rustc_query_system",
  "rustc_serialize",

compiler/rustc_query_impl/Cargo.toml

@@ -13,7 +13,6 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
-rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_query_system = { path = "../rustc_query_system" }
 rustc-rayon-core = { version = "0.5.0", optional = true }