message: dcsctp: fixed grammar in one comment, added comment regarding the threading contract
  Cr-Commit-Position: refs/heads/master@{#34788}
diff: @@ -205,7 +205,7 @@ struct Metrics {
  absl::optional<uint32_t> peer_rwnd_bytes = absl::nullopt;
  };
  -// Callbacks that the DcSctpSocket will be done synchronously to the owning
  +// Callbacks that the DcSctpSocket will call synchronously to the owning
  // client. It is allowed to call back into the library from callbacks that start
  // with "On". It has been explicitly documented when it's not allowed to call
  // back into this library from within a callback.
  @@ -339,6 +339,7 @@ class DcSctpSocketCallbacks {
  };
  // The DcSctpSocket implementation implements the following interface.
  +// This class is thread-compatible.
  class DcSctpSocketInterface {
  public:
  virtual ~DcSctpSocketInterface() = default;
  