chore(ci): bump actions-rust-lang/setup-rust-toolchain to v1.15.4

Author: luisschwab

.github/workflows/audit.yml

@@ -12,7 +12,7 @@ on:
       - '**/Cargo-recent.lock'
       - '**/Cargo-minimal.lock'
   schedule:
-    - cron: '0 0 * * 0' # At 00:00 on Sunday
+    - cron: '0 0 * * 0' # Sunday @ 00:00:00 UTC
   workflow_dispatch:
 env:
   CARGO_TERM_COLOR: always
@@ -35,7 +35,7 @@ jobs:
           persist-credentials: false
 
       - name: Install Rust toolchain and configure cache
-        uses: actions-rust-lang/setup-rust-toolchain@1780873c7b576612439a134613cc4cc74ce5538c # v1
+        uses: actions-rust-lang/setup-rust-toolchain@2b1f5e9b395427c92ee4e3331786ca3c37afe2d7 # v1.15.4
         with:
           toolchain: stable
           cache: true