treewide: bump rules_rust to 0.56.0

Change-Id: I7e1ee6f6d10d1ffe0b8e94f81b4a901f49bf818d
Reviewed-on: https://review.monogon.dev/c/monogon/+/3765
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/build/rust/BUILD.bazel b/build/rust/BUILD.bazel
index 355b394..f34a1cd 100644
--- a/build/rust/BUILD.bazel
+++ b/build/rust/BUILD.bazel
@@ -1,5 +1,5 @@
-load("@rules_rust//proto/prost:defs.bzl", "rust_prost_toolchain")
 load("@rules_rust//rust:defs.bzl", "rust_library_group")
+load("@rules_rust_prost//:defs.bzl", "rust_prost_toolchain")
 
 rust_library_group(
     name = "prost_runtime_efi",
@@ -23,5 +23,5 @@
 toolchain(
     name = "prost_efi_toolchain",
     toolchain = "prost_efi_toolchain_impl",
-    toolchain_type = "@rules_rust//proto/prost:toolchain_type",
+    toolchain_type = "@rules_rust_prost//:toolchain_type",
 )