test: fix melpazoid build to use emacs25

.travis.yml

@@ -1,17 +1,13 @@
+dist: focal
 sudo: required
 language: python
 python: ['3.6']
 install:
   - emacs --version
-  - yes '' | sudo add-apt-repository ppa:kelleyk/emacs
-  - sudo apt update
-  - sudo apt install emacs25-nox
-  - echo `dpkg -L emacs25-nox`
   - git clone https://github.com/riscy/melpazoid.git ~/melpazoid
   - pip install ~/melpazoid
 env:
   - RECIPE='(shx :repo "riscy/shx-for-emacs" :fetcher github)' EXIST_OK=true
 script:
   - emacs -Q --script ./test/script.el
-  - emacs25 -Q --script ./test/script.el
   - make -C ~/melpazoid