Remove cache_root property reference

Change-Id: I2bb02a7610f27e489ecde946055a6c9670615f2f
Bug: https://github.com/flutter/flutter/issues/143671
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/55401
Reviewed-by: Ricardo Amador <ricardoamador@google.com>
Commit-Queue: Keyong Han <keyonghan@google.com>
diff --git a/recipes/engine_v2/cache.py b/recipes/engine_v2/cache.py
index 0d1a5d4..5141b0e 100644
--- a/recipes/engine_v2/cache.py
+++ b/recipes/engine_v2/cache.py
@@ -19,20 +19,19 @@
   # Engine path is used inconsistently across the engine repo. We'll start
   # with [cache]/builder and will adjust it to start using it consistently.
   env['ENGINE_PATH'] = api.path['cache'].join('builder')
-  cache_root = api.properties.get('cache_root', 'CACHE')
   cache_ttl = api.properties.get('cache_ttl', 3600 * 4)
   cache_name = api.properties.get('cache_name')
 
   if api.cache.requires_refresh(cache_name):
     api.repo_util.engine_checkout(builder_root, env, env_prefixes)
     paths = [
-        api.path[cache_root].join(p)
+        api.path['cache'].join(p)
         for p in api.properties.get('cache_paths', [])
     ]
 
     api.path.mock_add_directory(api.path['cache'].join('builder', 'fake'))
     ignore_paths = [
-        api.path[cache_root].join(p)
+        api.path['cache'].join(p)
         for p in api.properties.get('ignore_cache_paths', [])
     ]