Slightly clarify pepper value

proposals/2134-identity-hash-lookup.md

@@ -107,8 +107,8 @@ GET /_matrix/identity/v2/hash_details
 The name `lookup_pepper` was chosen in order to account for pepper values
 being returned for other endpoints in the future. The contents of
 `lookup_pepper` MUST match the regular expression `[a-zA-Z0-9]+`, whether
-hashing is being performed or not. When no hashing is occuring, a pepper
-value of at least length 1 is still required.
+hashing is being performed or not. When no hashing is occuring, a valid
+pepper value of at least length 1 is still required.
 
 If hashing, the client appends the pepper to the end of the 3PID string,
 after a space.