ci: Pin GitHub Actions to commit SHAs for s3-tables-tests

Update all action refs to use pinned commit SHAs instead of floating tags:
- actions/checkout: @v6 → @8e8c483 (v4)
- actions/setup-go: @v6 → @0c52d54 (v5)
- actions/upload-artifact: @v6 → @65d8626 (v4)

Pinned SHAs improve reproducibility and reduce supply chain risk by
preventing accidental or malicious changes in action releases. Aligns
with repository conventions used in other workflows (e.g., go.yml).

.github/workflows/s3-tables-tests.yml

@@ -19,10 +19,10 @@ jobs:
     
     steps:
       - name: Check out code
-        uses: actions/checkout@v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v4
 
       - name: Set up Go
-        uses: actions/setup-go@v6
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5
         with:
           go-version-file: 'go.mod'
         id: go
@@ -63,7 +63,7 @@ jobs:
 
       - name: Upload test logs on failure
         if: failure()
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@65d862660abb392b6f0d302f3c50230a4d21cb92 # v4
         with:
           name: s3-tables-test-logs
           path: test/s3tables/test-output.log
@@ -76,10 +76,10 @@ jobs:
     
     steps:
       - name: Check out code
-        uses: actions/checkout@v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v4
 
       - name: Set up Go
-        uses: actions/setup-go@v6
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5
         with:
           go-version-file: 'go.mod'
         id: go
@@ -121,10 +121,10 @@ jobs:
     
     steps:
       - name: Check out code
-        uses: actions/checkout@v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v4
 
       - name: Set up Go
-        uses: actions/setup-go@v6
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5
         with:
           go-version-file: 'go.mod'
         id: go
@@ -160,10 +160,10 @@ jobs:
     
     steps:
       - name: Check out code
-        uses: actions/checkout@v6
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v4
 
       - name: Set up Go
-        uses: actions/setup-go@v6
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5
         with:
           go-version-file: 'go.mod'
         id: go