(maint) install curl on runners

Author: eputnam

.github/workflows/unit-test.yml

@@ -10,6 +10,10 @@ jobs:
         with:
           ruby-version: 2.6
           bundler-cache: false
+      - name: install curl
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y curl
       - name: Run bundle install
         run: bundle install
       - name: Uninstall docker
@@ -29,6 +33,10 @@ jobs:
         with:
           ruby-version: 2.6
           bundler-cache: false
+      - name: install curl
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y curl
       - name: Run bundle install
         run: bundle install
       - name: Uninstall podman