chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/audit.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: audit
         uses: actions-rs/audit-check@v1

.github/workflows/lint.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: cache cargo
         uses: actions/cache@v2

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: cache cargo
         uses: actions/cache@v2