Add missing sudo.

.github/workflows/doc.yml

@@ -15,7 +15,7 @@ jobs:
 # Build doc #
 #############
   build:
-    name: Make HTML doc
+    name: Make doc
     continue-on-error: false
     runs-on: ubuntu-latest
 
@@ -26,7 +26,7 @@ jobs:
       - name: Install dependencies
         run: |
           pip3 install -r doc/requirements.txt
-          apt-get -y install latexmk
+          sudo apt-get -y install latexmk
 
       - name: Build doc
         run: |