Bump version to libgdbm6

Author: hsbt

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
       if: ${{ matrix.os == 'ubuntu-latest' }}
       run: |
         sudo apt update -qy
-        sudo apt install libgdbm5 libgdbm-dev
+        sudo apt install libgdbm6 libgdbm-dev
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: