add tex-gyre package for tgtermes.sty

This change fixes the pdf-docs job by installing
tex-gyre to provide the missing tgtermes.sty style.

Change-Id: I885ed9153d9ccd9d3a486b5fc573238520474592

roles/prepare-build-pdf-docs/tasks/main.yaml

@@ -10,6 +10,9 @@
       - latexmk
       - texlive-xetex
       - texlive-fonts-recommended
+      # Required for tgtermes.sty style, this is a recommended package
+      # for texlive-fonts-recommended but it is not installed by default.
+      - tex-gyre
       - cm-super
       - fonts-liberation
       - inkscape