Previously, the Get repository content REST API endpoint had a file size limit of 1 MB. That didn’t correspond to the Create or update file contents endpoint which has a file size limit of 100 MB. Now, both endpoints have a file size limit of 100 MB. However, requests for file contents larger than 1 MB must include the .raw custom media type in the Accept HTTP header, as shown here:

Accept: application/vnd.github.v3.raw

Read more about GitHub's REST API endpoints for repository contents.