docs: fix broken example in config.md

Bug: https://github.com/google/perfetto/issues/38
Change-Id: I584643cbd3807b114af16bf042e2f155d1fcadb2

docs/concepts/config.md

diff --git a/docs/concepts/config.md b/docs/concepts/config.md
index 1f8d37e..cb15859 100644
--- a/docs/concepts/config.md
+++ b/docs/concepts/config.md
@@ -359,11 +359,10 @@
 data_sources {
   config {
     name: "track_event"
-
-    # Enable the data source only on Chrome and Chrome canary.
-    producer_name_filter: "com.android.chrome"
-    producer_name_filter: "com.google.chrome.canary"
   }
+  # Enable the data source only on Chrome and Chrome canary.
+  producer_name_filter: "com.android.chrome"
+  producer_name_filter: "com.google.chrome.canary"
 }
 ```