Merge pull request #20756 from grpc/vjpai-patch-1

Fix outdated comment

src/core/lib/transport/metadata.h

@@ -37,11 +37,8 @@ extern grpc_core::DebugOnlyTraceFlag grpc_trace_metadata;
 /* This file provides a mechanism for tracking metadata through the grpc stack.
    It's not intended for consumption outside of the library.
 
-   Metadata is tracked in the context of a grpc_mdctx. For the time being there
-   is one of these per-channel, avoiding cross channel interference with memory
-   use and lock contention.
-
-   The context tracks unique strings (grpc_mdstr) and pairs of strings
+   Metadata is tracked in the context of a sharded global grpc_mdctx. The
+   context tracks unique strings (grpc_mdstr) and pairs of strings
    (grpc_mdelem). Any of these objects can be checked for equality by comparing
    their pointers. These objects are reference counted.