Update actions/checkout action to v6

Author: oxide-renovate[bot]

.github/workflows/rust.yml

@@ -10,7 +10,7 @@ jobs:
   check_fmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - uses: actions-rs/toolchain@16499b5e05bf2e26879000db0c1d13f7e13fa3af # v1
         with:
           toolchain: stable
@@ -22,7 +22,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - uses: actions-rs/toolchain@16499b5e05bf2e26879000db0c1d13f7e13fa3af # v1
         with:
           toolchain: stable
@@ -34,7 +34,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - uses: actions-rs/toolchain@16499b5e05bf2e26879000db0c1d13f7e13fa3af # v1
         with:
           toolchain: stable