Disable building latex documentation on ci.

The documentation currently fails to build on Jenkins due to
hyperref and doxygen not playing nicely with each other on
Debian Stretch.

ci/autotools.sh

@@ -61,4 +61,5 @@ make
 make distcheck PKG_CONFIG_PATH=${PKG_CONFIG_PATH}
 
 # build the documentation
-make -C doc/latex
+# currently fails on jenkins (debian stretch)
+# make -C doc/latex

ci/unix.sh

@@ -19,4 +19,5 @@ make -C unix PKG_CONFIG_PATH=$PWD/../opus check
 
 # build the documentation
 make -C doc
-make -C doc/latex
+# currently fails on jenkins (debian stretch)
+# make -C doc/latex