@Vardhan Reddy Logic app already have the DevpOs connector which you can leverage to perform different operations. This connector already has the Send an HTTP request to Azure DevOps where you can build the request as per the DevOps REST API document in case if the action is not available.
If you are getting 401 error, then make sure you have Third-party application access via OAuth
option enabled. For more screenshots and details refer to this.
Just for your reference I have tested the request and created the repository in my project as per the screenshot below.
Make sure you are building the request and request URI correctly else you may get 401 error if you are hitting the wrong endpoint.
For any assistance on DevOps API you can you to always reach out to DevOps experts below as DevOps is not supported in Microsoft QnA currently.
https://stackoverflow.com/questions/tagged/devops
https://developercommunity.visualstudio.com/spaces/21/index.html
In case if you need any assistance from the logic app end then feel free to get back to me.
Please "Accept Answer" if the answer is helpful so that it can help others in the community.