Update rand to deduplicate it

Author: lqd

Diff for: Cargo.lock

@@ -4052,7 +4052,7 @@ dependencies = [
 name = "rustc_incremental"
 version = "0.0.0"
 dependencies = [
- "rand 0.7.3",
+ "rand 0.8.4",
  "rustc_ast",
  "rustc_data_structures",
  "rustc_errors",

Diff for: compiler/rustc_incremental/Cargo.toml

@@ -9,7 +9,7 @@ doctest = false
 [dependencies]
 rustc_graphviz = { path = "../rustc_graphviz" }
 tracing = "0.1"
-rand = "0.7"
+rand = "0.8.4"
 rustc_middle = { path = "../rustc_middle" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }