Get rid of the build matrix

Just build Rocq latest

Author: tchajed

.github/workflows/ci.yml

@@ -8,10 +8,6 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        rocq-version: ["latest"]
-      fail-fast: false
     steps:
       - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
@@ -20,7 +16,7 @@ jobs:
       - name: Install Rocq
         uses: tchajed/setup-rocq@v1
         with:
-          rocq-version: "${{ matrix.rocq-version }}"
+          rocq-version: latest
       - name: Install dependencies
         run: |
           opam pin add --no-action .