ci: bump Buildroot to 2026.02 for Go 1.25 support

ShellHub 0.21.5 requires Go >= 1.24.9 but Buildroot 2024.11 only
ships Go 1.23.2. Bump to Buildroot 2026.02 which includes Go 1.25.7.

Author: gustavosbarreto

.github/workflows/ci.yml

@@ -74,7 +74,7 @@ jobs:
 
       - name: Clone Buildroot
         run: |
-          git clone --depth 1 --branch 2024.11 https://github.com/buildroot/buildroot.git /tmp/buildroot
+          git clone --depth 1 --branch 2026.02 https://github.com/buildroot/buildroot.git /tmp/buildroot
 
       - name: Cache Buildroot downloads
         uses: actions/cache@v4