TODO comment cleanup.

Summary:
These are either no longer relevant, are unlikely to be done, or are spculative enough that they don't deserve code space.

Hope here is to make our search for TODOs higher signal.

Reviewed By: lnicco

Differential Revision: D29769792

fbshipit-source-id: 7cfa62cdc15e72d8b7b0cd5dbb5913ea3ca3dc5a

quic/state/SimpleFrameFunctions.cpp

@@ -243,7 +243,6 @@ bool updateSimpleFrameOnPacketReceived(
       return true;
     }
     case QuicSimpleFrame::Type::KnobFrame: {
-      // TODO it's const so we have to copy it
       const KnobFrame& knobFrame = *frame.asKnobFrame();
       conn.pendingEvents.knobs.emplace_back(
           knobFrame.knobSpace, knobFrame.id, knobFrame.blob->clone());