triagebot: label tidy changes with a more specific A-tidy label

Author: jieyouxu

triagebot.toml

@@ -417,12 +417,16 @@ trigger_files = [
     "src/ci",
     "src/tools/compiletest",
     "src/tools/cargotest",
-    "src/tools/tidy",
     "src/tools/remote-test-server",
     "src/tools/remote-test-client",
     "src/tools/tier-check"
 ]
 
+[autolabel."A-tidy"]
+trigger_files = [
+    "src/tools/tidy",
+]
+
 [autolabel."A-meta"]
 trigger_files = [
     "triagebot.toml",