docs: remove Molecule from contributions section (#881)

Molecule has not supported Goss for some time.

Fixes: #880

README.md

@@ -313,7 +313,6 @@ Full list of available Json schema validators can be found in <https://json-sche
 * [degoss](https://github.com/naftulikay/ansible-role-degoss) - Ansible role for installing, running, and removing Goss in a single go.
 * [kitchen-goss](https://github.com/ahelal/kitchen-goss) - A test-kitchen verifier plugin for Goss.
 * [goss-fpm-files](https://github.com/deanwilson/unixdaemon-fpm-cookery-recipes) - Might be useful for building goss system packages.
-* [molecule](https://github.com/metacloud/molecule) - Automated testing for Ansible roles, with native Goss support.
 * [packer-provisioner-goss](https://github.com/YaleUniversity/packer-provisioner-goss) - A packer plugin to run Goss as a provision step.
 * [gossboss](https://github.com/mdb/gossboss) - Collect and view aggregated Goss test results from multiple remote Goss servers.
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