Bump pipeline to actions/checkout@v4

Removing aws-{access-key-id,secret-access-key} in commit
12d0c492e8a41626a88c391cec68402d90bd6427 did the trick!

- https://github.com/mbland/elistman/actions/runs/6150947953/job/16690000086

So my guess is that `sam pipeline` and its workshop was updated to use
OIDC since I'd run it originally:

- https://catalog.workshops.aws/complete-aws-sam/en-US/module-4-cicd/module-4-cicd-gh/50-sampipeinit

Hence, I think the previous AWS credentials were at odds with the new
pipeline execution role trust config, which expected a GitHub OIDC
token. Having the old credential items present must've disabled the OIDC
mechanism, and AWS rejected the request because it didn't use OIDC.

I've also since removed the AWS_{ACCESS_KEY_ID,SECRET_ACCESS_KEY}
repository secrets as well. This change should trigger a passing run.

.github/workflows/pipeline.yaml

@@ -44,7 +44,7 @@ jobs:
     if: startsWith(github.event.ref, 'feature') && github.event_name == 'delete'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: aws-actions/setup-sam@v2
         with:
           use-installer: true
@@ -75,7 +75,7 @@ jobs:
     needs: [test]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: aws-actions/setup-sam@v2
         with:
           use-installer: true
@@ -113,7 +113,7 @@ jobs:
     needs: [test]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: aws-actions/setup-sam@v2
         with:
           use-installer: true
@@ -176,7 +176,7 @@ jobs:
     needs: [build-and-package]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: aws-actions/setup-sam@v2
         with:
           use-installer: true
@@ -212,7 +212,7 @@ jobs:
     needs: [deploy-testing]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run smoke tests
         run: |
           tr -d '\r' > .env <<EOF
@@ -228,7 +228,7 @@ jobs:
     # https://docs.github.com/en/actions/reference/environments
     # environment: <configured-environment>
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: aws-actions/setup-sam@v2
         with:
           use-installer: true

.github/workflows/run-tests.yaml

@@ -7,7 +7,7 @@ jobs:
     name: "Run Tests"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Go
         uses: actions/setup-go@v4