[CI][XML] Added XMLLINT to CI Dependencies

A warning was being generated by EZGL when pre-processing the resources
for main.ui. This could not be removed since the library we use to
preprocess always tries to use XMLLINT even when it is not used.

If the system does not have XMLLINT installed, it will always give a
warning saying it is not installed.

As a quick fix, we can make it so the CI has it installed, since this is
technically the use case we want tested.

Author: AlexandreSinger

.github/scripts/install_dependencies.sh

@@ -29,6 +29,7 @@ sudo apt install -y \
   libncurses5-dev \
   libx11-dev \
   libxft-dev \
+  libxml2-utils \
   libxml++2.6-dev \
   libreadline-dev \
   tcllib \