Fix tidy error

Author: bjorn3

compiler/rustc_type_ir/Cargo.toml

@@ -10,8 +10,8 @@ derivative = "2.2.0"
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
-rustc_span = { path = "../rustc_span", optional = true }
 rustc_serialize = { path = "../rustc_serialize", optional = true }
+rustc_span = { path = "../rustc_span", optional = true }
 smallvec = { version = "1.8.1" }
 # tidy-alphabetical-end
 
@@ -21,8 +21,8 @@ nightly = [
     "smallvec/may_dangle",
     "smallvec/union",
     "rustc_index/nightly",
-    "rustc_span",
     "rustc_serialize",
+    "rustc_span",
     "rustc_data_structures",
     "rustc_macros",
 ]