ORC-2118: Use ubuntu-slim for GitHub Actions license-check job

### What changes were proposed in this pull request?

This PR aims to use `ubuntu-slim` for GitHub Actions `license-check` job

### Why are the changes needed?

`ubuntu-slim` is a new cost-efficient runner to fit small jobs like `license-check`. We had better use this to save ASF infra usage (if possible)
- https://github.blog/changelog/2025-10-28-1-vcpu-linux-runner-now-available-in-github-actions-in-public-preview/
- https://github.com/actions/runner-images/blob/main/images/ubuntu-slim/ubuntu-slim-Readme.md

| Feature | `ubuntu-slim` | `ubuntu-latest` |
| :--- | :---: | :---: |
| **Cost (per minute)** | **$0.002** | **$0.012** |
| **Cost for 1,000 mins** | **$2.00** | **$12.00** |
| **CPU** | 1 vCPU | 4 vCPU |
| **Memory (RAM)** | 5 GB | 16 GB |
| **Storage (SSD)** | 14 GB | 14 GB |
| **Maximum Runtime** | **15 Minutes** | 6 Hours |
| **Isolation Type** | Container-based (L2) | Dedicated VM |

### How was this patch tested?

Pass the CIs.

- https://github.com/apache/orc/actions/runs/22474009738/job/65097036746?pr=2566

<img width="369" height="226" alt="Screenshot 2026-02-26 at 21 32 08" src="https://github.com/user-attachments/assets/9ed38fef-7e92-4fc8-bd11-ed923c9fd5f3" />

### Was this patch authored or co-authored using generative AI tooling?

Generated-by: `Gemini 3.1 Pro (High)` on `Antigravity`

Closes #2566 from dongjoon-hyun/ORC-2118.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

.github/workflows/build_and_test.yml

@@ -249,7 +249,7 @@ jobs:
 
   license-check:
     name: "License Check"
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     steps:
       - name: Checkout repository
         uses: actions/checkout@v6