unabbreviate a title in readme

Change-Id: Id493d8de94313c3fcc109614915433c08682a250
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/13220
Reviewed-by: Christopher Fujino <fujino@google.com>
Commit-Queue: Yegor Jbanov <yjbanov@google.com>

README.md

diff --git a/README.md b/README.md
index d25c515..dda85a9 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 config, see [flutter/infra on GitHub](https://github.com/flutter/infra). Actual
 builds can be seen at [ci.chromium.org](https://ci.chromium.org/p/flutter).
 
-## Config
+## Configuration
 
 [Tricium](https://chromium.googlesource.com/infra/infra/+/master/go/src/infra/tricium/README.md) configurations recipes repo.