Do not update package info in CI workflow

It also reverts f58bad4. The use of OCaml 4.09.1 does not seem to
be the real cause of the long set up time.

.github/workflows/kind2-ci.yml

@@ -12,13 +12,12 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-20.04, macos-11 ]
+        ocaml-version: [ 4.09.1 ]
         include:
           - os: macos-11
-            ocaml-version: 4.14.1
             pkg_update: brew update
             z3_install: brew install z3
           - os: ubuntu-20.04
-            ocaml-version: 4.09.1
             pkg_update: sudo apt-get update -y
             z3_install: sudo apt-get install -y z3
 
@@ -28,8 +27,8 @@ jobs:
     - name: Checkout code
       uses: actions/checkout@v3
 
-    - name: Update package information
-      run: ${{ matrix.pkg_update }}
+    #- name: Update package information
+    #  run: ${{ matrix.pkg_update }}
 
     - name: Set up OCaml ${{ matrix.ocaml-version }}
       uses: ocaml/setup-ocaml@v2