Update GitHub action; see if I can use Go 1.24 directly

Author: ahamlinman

.github/workflows/mainline.yml

@@ -7,13 +7,13 @@ on:
     branches: [main]
 jobs:
   mainline:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
     - name: Checkout
       uses: actions/checkout@v4
     - name: Install Go
       uses: actions/setup-go@v5
-      with: { go-version: "1.22" }
+      with: { go-version: "1.24" }
     - name: Run Tests
       run: go test -v -race ./...
     - name: Set up Docker Buildx