remove a few more TODOs

csharp/src/Google.Protobuf/Collections/MapField.cs

@@ -446,7 +446,6 @@ namespace Google.Protobuf.Collections
         [SecuritySafeCritical]
         public void AddEntriesFrom(ref ParseContext ctx, Codec codec)
         {
-            // TODO: deduplicate code?
             var adapter = new Codec.MessageAdapter(codec);
             do
             {

csharp/src/Google.Protobuf/ParserInternalState.cs

@@ -82,8 +82,8 @@ namespace Google.Protobuf
         
         internal SegmentedBufferHelper segmentedBufferHelper;
 
-        // TODO: remember if this context is supposed to call MergeFrom(CodedInputStream cis) or MergeFrom(ref ParseContext ....) for submessages.
-        // if non-null, the top level parse method was started with given cis as an argument
+        // If non-null, the top level parse method was started with given coded input stream as an argument
+        // which also means we can potentially fallback to calling MergeFrom(CodedInputStream cis) if needed.
         internal CodedInputStream codedInputStream;
         
         
@@ -99,7 +99,7 @@ namespace Google.Protobuf
         internal uint nextTag;
         internal bool hasNextTag;
 
-        // TODO: these fields are configuration, they should be readonly
+        // these fields are configuration, they should be readonly
         internal int sizeLimit;
         internal int recursionLimit;
         

csharp/src/Google.Protobuf/UnknownFieldSet.cs

@@ -186,7 +186,6 @@ namespace Google.Protobuf
         /// <returns>false if the tag is an "end group" tag, true otherwise</returns>
         private bool MergeFieldFrom(ref ParseContext ctx)
         {
-            // TODO: deduplicate MergeFieldFrom implementations
             uint tag = ctx.LastTag;
             int number = WireFormat.GetTagFieldNumber(tag);
             switch (WireFormat.GetTagWireType(tag))