ci: build linux_amd64 on depot-ubuntu-24.04-16 for faster CI

Override the upstream extension-distribution workflow's runner matrix to
build linux_amd64 on a 16-core Depot runner instead of GitHub's default
4-core ubuntu-24.04. The C++/vcpkg compile is CPU-bound and parallelizes
well, so this should significantly cut wall-clock time.

linux_arm64 stays on GitHub's ubuntu-24.04-arm pending confirmation that
the org has Depot ARM runners enabled.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: bill-ph

.github/workflows/MainDistributionPipeline.yml

@@ -32,6 +32,8 @@ jobs:
       duckdb_version: ${{ needs.get-duckdb-version.outputs.duckdb_version }}
       ci_tools_version: main
       extension_name: ducklake
+      runners: |
+        {"linux_amd64": "depot-ubuntu-24.04-16", "linux_arm64": "ubuntu-24.04-arm"}
 
   duckdb-next-deploy:
     name: Deploy extension binaries