Move the tokio-dispatcher build from amd64-ci-small to amd64-ci-medium

It was the last user of the 4-CPU class. #10653 already moved
the Rust docs job to its own amd64-ci-docs runner.

Signed-off-by: Claude <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014DcoycxoTMpyz66pmby8Nb

Author: robert3005

.github/workflows/ci.yml

@@ -327,7 +327,7 @@ jobs:
             runner: amd64-ci-large
             args: "--all-targets"
           - name: "with tokio dispatcher"
-            runner: amd64-ci-small
+            runner: amd64-ci-medium
             # Only build the crates that have the tokio features, not re-building other crates with no-default-features
             args: "--no-default-features --features tokio --all-targets -p vortex -p vortex-io -p vortex-file -p vortex-layout"
           - name: "wasm32 with default features"