fix(docs): standardize terminology for payment non-existence in FAssets redemption guide

Author: fassko

docs/fassets/developer-guides/7-fassets-redeem.mdx

@@ -338,8 +338,8 @@ These [operational parameters](/fassets/operational-parameters) define the timef
 
 If the agent is unable to pay the redemption payment in the specified time, the redeemer can:
 
-1. Make a proof of [payment non existence](/fdc/attestation-types/referenced-payment-nonexistence) using the [Flare Data Connector](/fdc/overview).
-2. Execute the [`redemptionPaymentDefault`](/fassets/reference/IAssetManager#redemptionpaymentdefault) function and present the proof of payment non existence to the FAssets system, which triggers a redemption failure.
+1. Make a proof of [payment non-existence](/fdc/attestation-types/referenced-payment-nonexistence) using the [Flare Data Connector](/fdc/overview).
+2. Execute the [`redemptionPaymentDefault`](/fassets/reference/IAssetManager#redemptionpaymentdefault) function and present the proof of payment non-existence to the FAssets system, which triggers a redemption failure.
 3. The redeemer receives collateral plus a premium.
 
 ## Summary