Use matrix for ubuntu

.github/workflows/ci.yml

@@ -7,23 +7,15 @@ on:
   pull_request:
     branches:
       - master
+
 jobs:
-  test-ubuntu-latest:
+  test-ubuntu:
-    runs-on: ubuntu-latest
+    strategy:
-    steps:
+      matrix:
-      - uses: actions/checkout@v2
+        ubuntu:
-      - name: install test dependencies
+          - 16.04
-        run: sudo apt-get install libtest-warnings-perl
+          - latest
-      - name: autogen
+    runs-on: ubuntu-${{ matrix.ubuntu }}
-        run: ./autogen
-      - name: configure
-        run: ./configure
-      - name: check
-        run: make check
-      - name: distcheck
-        run: make distcheck
-  test-ubuntu-oldest:
-    runs-on: ubuntu-16.04
     steps:
       - uses: actions/checkout@v2
       - name: install test dependencies