clarify pruning issue (#886)

Signed-off-by: Ratan Rai Sur <ratan.r.sur@gmail.com>

KNOWN_ISSUES.md

@@ -24,11 +24,10 @@ A fix for this issue is being actively worked on.
 ## Error full syncing with pruning
 
 - Error syncing with mainnet on Besu 1.3.7 node - MerkleTrieException [\#580](https://github.com/hyperledger/besu/issues/580)
-The associated error is `Unable to load trie node value for hash` and is caused by the combination of
-full sync and pruning.
+The associated error is `Unable to load trie node value for hash`.
 
 Workarounds:
-1. Explicitly disable pruning using `--pruning-enabled=false` when using fast sync.
+1. Explicitly disable pruning using `--pruning-enabled=false` when using fast sync. It is already disabled by default for full sync.
 2. If the `MerkleTrieException` occurs, delete the database and resync.
 
 A fix for this issue is being actively worked on.
@@ -63,4 +62,4 @@ Workaround -> When using onchain permissioning, ensure bootnodes are also valida
 A critical issue for privacy users with private transactions created using Hyperledger Besu v1.3.4 
 or earlier has been identified. If you have a network with private transaction created using v1.3.4 
 or earlier, please read the following and take the appropriate steps: 
-https://wiki.hyperledger.org/display/BESU/Critical+Issue+for+Privacy+Users 
+https://wiki.hyperledger.org/display/BESU/Critical+Issue+for+Privacy+Users