fix: use exclude regex for generated sources

exclude_paths uses prefix matching from the project root, so
"src/main/generated/" did not match the nested path
"prometheus-metrics-exposition-formats/src/main/generated/".
Switch to exclude (regex, substring match) which works for any depth.
Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/config/flint.toml

@@ -1,7 +1,7 @@
 [settings]
+exclude = "src/main/generated"
 exclude_paths = [
     "docs/themes/",
-    "src/main/generated/",
     "mvnw",
 ]