docs: remove mentions of coral, it's not implemented

dht.go

 // Package dht implements a distributed hash table that satisfies the ipfs routing
-// interface. This DHT is modeled after kademlia with Coral and S/Kademlia modifications.
+// interface. This DHT is modeled after kademlia with S/Kademlia modifications.
 package dht
 
 import (
@@ -40,7 +40,7 @@ var ProtocolDHTOld protocol.ID = "/ipfs/dht"
 // collect members of the routing table.
 const NumBootstrapQueries = 5
 
-// IpfsDHT is an implementation of Kademlia with Coral and S/Kademlia modifications.
+// IpfsDHT is an implementation of Kademlia with S/Kademlia modifications.
 // It is used to implement the base IpfsRouting module.
 type IpfsDHT struct {
 	host      host.Host        // the network services we need

dht_bootstrap.go

 // Package dht implements a distributed hash table that satisfies the ipfs routing
-// interface. This DHT is modeled after kademlia with Coral and S/Kademlia modifications.
+// interface. This DHT is modeled after Kademlia with S/Kademlia modifications.
 package dht
 
 import (

pb/dht.pb.go

@@ -116,6 +116,7 @@ type Message struct {
 	// defines what type of message it is.
 	Type *Message_MessageType `protobuf:"varint,1,opt,name=type,enum=dht.pb.Message_MessageType" json:"type,omitempty"`
 	// defines what coral cluster level this query/response belongs to.
+	// in case we want to implement coral's cluster rings in the future.
 	ClusterLevelRaw *int32 `protobuf:"varint,10,opt,name=clusterLevelRaw" json:"clusterLevelRaw,omitempty"`
 	// Used to specify the key associated with this message.
 	// PUT_VALUE, GET_VALUE, ADD_PROVIDER, GET_PROVIDERS

pb/dht.proto

@@ -50,6 +50,7 @@ message Message {
 	optional MessageType type = 1;
 
 	// defines what coral cluster level this query/response belongs to.
+	// in case we want to implement coral's cluster rings in the future.
 	optional int32 clusterLevelRaw = 10;
 
 	// Used to specify the key associated with this message.

routing.go

@@ -246,8 +246,9 @@ func (dht *IpfsDHT) GetValues(ctx context.Context, key string, nvals int) (_ []r
 	return vals, nil
 }
 
-// Value provider layer of indirection.
-// This is what DSHTs (Coral and MainlineDHT) do to store large values in a DHT.
+// Provider abstraction for indirect stores.
+// Some DHTs store values directly, while an indirect store stores pointers to
+// locations of the value, similarly to Coral and Mainline DHT.
 
 // Provide makes this node announce that it can provide a value for the given key
 func (dht *IpfsDHT) Provide(ctx context.Context, key *cid.Cid, brdcst bool) (err error) {