Update publish_site.yml

There are problems with libcurl4-openssl-dev mirrors.
As in [1]. Attempt with [2] solution.
[1] actions/runner-images#5470
[2] actions/runner-images#3640

.github/workflows/publish_site.yml

@@ -15,6 +15,7 @@ jobs:
 
       - name: Install tools
         run: |
+          sudo apt-get update
           sudo apt install -y pandoc libxml2-dev libssl-dev libcurl4-openssl-dev r-base r-base-dev;
           sudo apt install -y libharfbuzz-dev libfribidi-dev;
           sudo R -e "install.packages('devtools')";