docs: remove redundant words in comment (#6420)

Signed-off-by: cuibuwei <[email protected]>

docs/learn/learn-guides-identity.md

@@ -124,7 +124,7 @@ guidelines about clearing identities.
 **Clearing:** Users can clear their identity information and have their deposit returned. Clearing
 an identity also clears all sub accounts and returns their deposits.
 
-**Killing:** It is is possible to kill an identity that deems erroneous. This results in a slash of
+**Killing:** It is possible to kill an identity that deems erroneous. This results in a slash of
 the deposit.
 
 ## Setting Sub-Identities

docs/learn/learn-phragmen.md

@@ -9,7 +9,7 @@ slug: ../learn-phragmen
 
 ## NPoS Election Algorithms
 
-Since validators are paid almost equally in in each era, it is important that the stake behind each
+Since validators are paid almost equally in each era, it is important that the stake behind each
 validator is uniformly spread out. An election algorithm for Nominated Proof of Staking (NPoS) will
 try to optimize three metrics when computing a solution graph of nominators and validators:
 

docs/learn/learn-validator.md

@@ -27,7 +27,7 @@ trust-free environment.
 Parachain validators (i.e. para-validators) participate to the
 [Parachain Phase of the AnV Protocol](./learn-parachains-protocol.md/#parachain-phase), and submit
 [candidate receipts](./learn-parachains-protocol.md/#candidate-receipts) to the relay chain
-transaction queue so that a block author can include information on the parablock in a fork of of
+transaction queue so that a block author can include information on the parablock in a fork of
 the relay chain.
 
 Para-validators work in groups and are selected by the runtime in every epoch to validate parachain