Merge pull request #3163 from input-output-hk/td/fix-build

Update ruby version in github actions, in order to fix the build

.github/workflows/haskell.yml

@@ -23,10 +23,10 @@ jobs:
     steps:
     - uses: actions/checkout@v1
 
-    - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+    - name: Set up Ruby 2.7
+      uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.6
+        ruby-version: 2.7
 
     - name: Install cbor-diag and cddl
       run: |