You can uninstall or removes an installed fortran95-compiler package itself from Debian 9 (Stretch) through the terminal,
$ sudo apt-get remove fortran95-compiler
If you would like to remove fortran95-compiler and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove fortran95-compiler
If you use with purge options to fortran95-compiler package all the configuration and dependent packages will be removed.
$ sudo apt-get purge fortran95-compiler
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove fortran95-compiler