Fix typo in recipe name associated to platform.

Change-Id: Idc018aaa5fe2e54567e7d8bee974b462501111ce
Bug: https://github.com/flutter/flutter/issues/65223
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/6323
Reviewed-by: Keyong Han <keyonghan@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>
diff --git a/recipe_modules/shard_util/api.py b/recipe_modules/shard_util/api.py
index 9316639..1201c13 100644
--- a/recipe_modules/shard_util/api.py
+++ b/recipe_modules/shard_util/api.py
@@ -9,7 +9,7 @@
 # Builder names use full platform name instead of short names. We need to
 # map short names to full platform names to be able to identify the drone
 # used to run the subshards.
-PLATFORM_TO_NAME = {'win': 'Windows', 'linux': 'Linux', 'mac': 'mac'}
+PLATFORM_TO_NAME = {'win': 'Windows', 'linux': 'Linux', 'mac': 'Mac'}
 
 
 class ShardUtilApi(recipe_api.RecipeApi):