Fix capitalization in README.md (#16788)

diff --git a/packages/flutter_tools/README.md b/packages/flutter_tools/README.md
index a216eee..448faec 100644
--- a/packages/flutter_tools/README.md
+++ b/packages/flutter_tools/README.md
@@ -1,4 +1,4 @@
-# Flutter tools
+# Flutter Tools
 
 Tools for building Flutter applications.