Fix missing apt update in keiko github action (1.15) (#2747)

Co-authored-by: Jan Klopper <[email protected]>

.github/workflows/keiko_test.yml

@@ -9,9 +9,11 @@ on:
       - '*'
     paths:
       - keiko/**
+      - .github/workflows/keiko_test.yml
   pull_request:
     paths:
       - keiko/**
+      - .github/workflows/keiko_test.yml
 
 jobs:
   test:
@@ -34,7 +36,7 @@ jobs:
 
       - name: Install Latex
         run: |
-          sudo apt-get install -y --no-install-recommends \
+          sudo apt-get update && sudo apt-get install -y --no-install-recommends \
             chktex \
             fonts-recommended \
             latexmk \