ci: drop Go 1.14
Go 1.14 reached EOL and is not used by any of the three latest GitLab releases. This MR removes CI testing for 1.14, so that we can start relying on 1.15 features.
Go 1.14 reached EOL and is not used by any of the three latest GitLab releases. This MR removes CI testing for 1.14, so that we can start relying on 1.15 features.