ci: enable translated docs build in build-doc.sh

Pass --enable-build-documentation-translation to configure so the docs
CI builds the translated HTML/PDF set, not only English.  Exercises
the po4a / per-language pipeline end-to-end on every PR.

Author: grandixximo

.github/scripts/build-doc.sh

@@ -5,7 +5,9 @@ set -x
 
 cd src
 ./autogen.sh
-./configure --disable-check-runtime-deps --enable-build-documentation=html
+./configure --disable-check-runtime-deps \
+            --enable-build-documentation=html \
+            --enable-build-documentation-translation
 make -O -j$((1+$(nproc))) manpages
 make -O -j$((1+$(nproc))) translateddocs
 make -O -j$((1+$(nproc))) docs