[ci] Use custom sphinx-gallery in ci_gpu

To enable #10921 this builds sphinx-gallery using @guberti's changes

Author: driazati

docker/Dockerfile.ci_gpu

@@ -29,6 +29,10 @@ RUN bash /install/ubuntu_install_core.sh
 COPY install/ubuntu1804_install_python.sh /install/ubuntu1804_install_python.sh
 RUN bash /install/ubuntu1804_install_python.sh
 
+COPY install/ubuntu_install_sphinx.sh /install/ubuntu_install_sphinx.sh
+COPY install/sphinx_gallery_colab_fixes.patch /sphinx_gallery_colab_fixes.patch
+RUN bash /install/ubuntu_install_sphinx.sh
+
 # Globally disable pip cache
 RUN pip config set global.no-cache-dir false