Link to https://umn0mtkzgh5feerkye8f6wr.julianrbryant.com/ is dead

[heiderich]

The link to https://www.activemath.org/ seems to be dead in software/index.md

[kohlhase]

You are right, the whole page is almost obsolete (most of the links are dead by now) and we already have #7 for that.
Would you be willing to make a pull request that removes all the dead links?