Update README.md (#1251)

Author: thomasrockhu-codecov

README.md

@@ -11,6 +11,7 @@
 Breaking Changes
 - Tokenless uploading is unsupported. However, PRs made from forks to the upstream public repos will support tokenless (e.g. contributors to OS projects do not need the upstream repo's Codecov token)
 - Various arguments to the Action have been removed
+- For repositories using `Dependabot`, users will need to ensure that it has access to the Codecov token for PRs from Dependabot to upload coverage.
 
 `v3` versions and below will not have access to CLI features (e.g. global upload token, ATS).