docs/postmortems: fix spelling (ethereum#24558)

docs/postmortems/2021-08-22-split-postmortem.md

@@ -5,7 +5,7 @@ This is a post-mortem concerning the minority split that occurred on Ethereum ma
 ## Timeline
 
 
-- 2021-08-17: Guido Vranken submitted bounty report. Investigation started, root cause identified, patch variations discussed. 
+- 2021-08-17: Guido Vranken submitted a bounty report. Investigation started, root cause identified, patch variations discussed. 
 - 2021-08-18: Made public announcement over twitter about upcoming security release upcoming Tuesday. Downstream projects were also notified about the upcoming patch-release.
 - 2021-08-24: Released [v1.10.8](https://github.com/ethereum/go-ethereum/releases/tag/v1.10.8) containing the fix on Tuesday morning (CET). Erigon released [v2021.08.04](https://github.com/ledgerwatch/erigon/releases/tag/v2021.08.04).
 - 2021-08-27: At 12:50:07 UTC, issue exploited. Analysis started roughly 30m later, 
@@ -51,7 +51,7 @@ A memory-corruption bug within the EVM can cause a consensus error, where vulner
 
 #### Handling
 
-On the evening of 17th, we discussed options how to handle it. We made a state test to reproduce the issue, and verified that neither `openethereum`, `nethermind` nor `besu` were affected by the same vulnerability, and started a full-sync with a patched version of `geth`. 
+On the evening of 17th, we discussed options on how to handle it. We made a state test to reproduce the issue, and verified that neither `openethereum`, `nethermind` nor `besu` were affected by the same vulnerability, and started a full-sync with a patched version of `geth`. 
 
 It was decided that in this specific instance, it would be possible to make a public announcement and a patch release: