The package contains a debian/patches/series file usually used by quilt to apply patches at build time, but quilt is not listed in the build dependencies.
You should either remove the series file if it's effectively not useful or add quilt to the build-dependencies if quilt is used during the build process.
If you don't need quilt during build but only during maintenance work, then you can override this warning.
The tag is present in Lintian version
That is the most recent version we know about.
We use semantic versions.
The patch number is a commit step indicator relative to the
release tag in our Git
You can find the detection logic for this version at commit ffc17eb. For merge requests, please use the latest version in the Lintian check debian/patches/quilt.