fix tlmgr error message

using the latest docker image

.gitlab-ci.yml

 default:
   image:
-    name: pandoc/latex
+    name: pandoc/latex:latest
     entrypoint: [""]
   before_script:
     - apk add --no-cache build-base python3 python3-dev py3-pip ttf-freefont
@@ -21,4 +21,4 @@ make_pdf:
     - ./make-pdf.py
   artifacts:
     paths:
-      - "*.pdf"
\ No newline at end of file
+      - "*.pdf"