Remove conda recipe

Recipe moved to https://gitlab.com/tango-controls/conda/cpptango-feedstock

The conda package build is triggered using multi-project pipeline for any commit to the default branch.

Closes #1089 (closed)

To test, I removed the rules to trigger the job only on the default branch. Downstream pipeline was triggered properly: https://gitlab.com/tango-controls/cppTango/-/pipelines/858045880