CI: For cover use setup-beam because container breaks pip

.github/workflows/ci.yml

@@ -27,10 +27,11 @@ jobs:
     name: Cover
     needs: [tests]
     runs-on: ubuntu-22.04
-    container:
-      image: erlang:26
     steps:
     - uses: actions/checkout@v2
+    - uses: erlef/setup-beam@v1
+      with:
+        otp-version: 26
     - run: ./configure --enable-gcov
     - run: rebar3 compile
     - run: rebar3 eunit -v