docs(telemetry): drop plan-document pointers from consensus tracing comments

These comments pointed at a planning folder and at its rollout phase
numbering, neither of which is part of the shipped tree, so the
references would dangle for any reader of the repository. Each comment
now states the fact it was pointing at.

src/xrpld/app/consensus/RCLConsensus.cpp

@@ -274,9 +274,9 @@ RCLConsensus::Adaptor::propose(RCLCxPeerPos::Proposal const& proposal)
 
     app_.getHashRouter().addSuppression(suppression);
 
-    // Inject the current thread's active span context (e.g. the
-    // consensus round span from Phase 4) so receiving peers can link
-    // their proposal.receive span as a child of this trace.
+    // Inject the current thread's active span context (e.g. the consensus
+    // round span) so receiving peers can link their proposal.receive span
+    // as a child of this trace.
     telemetry::SpanGuard::injectCurrentContextToProtobuf(*prop.mutable_trace_context());
 
     app_.getOverlay().broadcast(prop);

src/xrpld/app/consensus/RCLConsensus.h

@@ -127,9 +127,9 @@ class RCLConsensus
          *
          *  Captured in makeAcceptSpan() and consumed by createValidationSpan()
          *  on the jtACCEPT worker thread so the validation.send span can be
-         *  follows-from linked to consensus.accept (matching the design doc
-         *  and span hierarchy diagram). Reset on each startRoundTracing()
-         *  to prevent a stale prior-round context from being linked.
+         *  follows-from linked to consensus.accept. Reset on each
+         *  startRoundTracing() to prevent a stale prior-round context from
+         *  being linked.
          *
          *  Thread safety: same model as roundSpanContext_. The write in
          *  makeAcceptSpan happens on the main consensus thread under

src/xrpld/telemetry/ConsensusReceiveTracing.h

@@ -34,7 +34,8 @@
  *
  * @note Span names come from the canonical constants in
  *  ConsensusSpanNames.h (consensus::span::proposalReceive /
- *  validationReceive) so they stay in sync with the rest of Phase 4.
+ *  validationReceive) so they stay in sync with the rest of the
+ *  consensus tracing surface.
  */
 
 #include <xrpl/consensus/ConsensusSpanNames.h>