Update to conan 2.0.4

README.md

conan-el6-gcc44-x86/.gitlab-ci.yml

conan-el6-gcc44-x86/Dockerfile

conan-el6-gcc44/.gitlab-ci.yml

conan-el6-gcc44/Dockerfile

conan-el6-gcc73-x86/.gitlab-ci.yml

conan-el6-gcc73-x86/Dockerfile

conan-el6-gcc73/.gitlab-ci.yml

conan-el6-gcc73/Dockerfile

conan-el6-gcc83-x86/.gitlab-ci.yml

conan-el6-gcc83-x86/Dockerfile

conan-el6-gcc83/.gitlab-ci.yml

conan-el6-gcc83/Dockerfile

conan-el6-gcc91-x86/.gitlab-ci.yml

conan-el6-gcc91-x86/Dockerfile

conan-el6-gcc91/.gitlab-ci.yml

conan-el6-gcc91/Dockerfile

conan-el7-gcc48-x86/.gitlab-ci.yml

conan-el7-gcc48-x86/Dockerfile

conan-el7-gcc48/.gitlab-ci.yml