No, the high priority feature cannot be disabled in the Q&A. However, you can use Question limits as a workaround to control or effectively prevent the high priority usage.
By setting the question limit of high priority questions to 0, Question Submitters will not able to submit new questions with high priority. Be aware that you will first need to set a (high) question limit of which 0 are high priority.
Note: This feature is not available for Basic subscriptions.
See example screen below: