Remove unused requirements.txt
Remove unused requirements.txt

In fdfa85711b15336ee666f2e6e239a740b4486902 we moved from requirements.txt to a
conda environment. This file has no current purpose except getting dependabot
to nag us about updates that don't matter because nobody is using it.

Removing the bitrotted file for clarity

e-mission/e-mission-server,e-mission/e-mission-server,shankari/e-mission-server,shankari/e-mission-server,e-mission/e-mission-server,shankari/e-mission-server,shankari/e-mission-server,e-mission/e-mission-server