To remove a skill proficiency requirement from a job, click on Jobs in the left navigation menu. On the Jobs page, locate the job for which you wish to remove the skill proficiency requirement and click on the name of the job.

By default, the Skills tab is selected. Locate the skill you wish to remove and click the orange wrench icon in the Edit column. (Be careful to click on the orange wrench icon associated with the skill and not the same icon for the job itself.) Next, click on the red wastebasket icon.

There will be no confirmation to delete the skill proficiency requirement but you will have a moment to undo the deletion.