typo fix

Signed-off-by: R.I.Pienaar <[email protected]>

adr/ADR-43.md

@@ -24,7 +24,7 @@ Related issues [#3268](https://github.com/nats-io/nats-server/issues/3268)
 ## Per-Message TTL
 
 We will allow a message to supply a TTL as a duration in a header called `Nats-TTL` followed by the duration as 
-nanoseconds, the sever may not supper nano second level precision and clients can choose to expose TTL as
+nanoseconds, the sever may not support nanosecond level precision and clients can choose to expose TTL as
 seconds or nanoseconds.
 
 The duration will be used by the server to calculate the deadline for removing the message based on its Stream