Update test/ARCHITECTURE.md

Co-authored-by: Martin Pitt <[email protected]>

test/ARCHITECTURE.md

@@ -255,8 +255,8 @@ allow for faster retrying.
 The `test/run` prepares an Virtual machine image for the given `TEST_OS` and then
 runs the tests by calling `test/common/run-tests` with the provided tests.
 
-For the Testing Farm (TF) scenario, Packit is responsible for setting up the
-test infrastructure and the entry point is `test/browser/browser.sh`. On TF we
+The [tmt](https://tmt.readthedocs.io) test is defined in [test/browser/main.fmf](./browser/main.fmf). These
+run on the Testing Farm (TF), triggered by [Packit](https://packit.dev/) for upstream PRs. On TF we
 get a single virtual machine without a hypervisor so tests run on the virtual
 machine directly this also implies that only `destructive` tests can be run.
 The `test/browser/browser.sh` script sets up the virtual machine and calls