fix typo

Co-authored-by: Hannes Tschofenig <[email protected]>

draft-ietf-uta-tls13-iot-profile.md

@@ -321,7 +321,7 @@ sections or even other specifications.
 ### Serial Number
 
 CAs MUST generate non-sequential serial numbers greater than or equal to eight
-(8) octects from a cryptographically secure pseudo-random number generator.
+(8) octets from a cryptographically secure pseudo-random number generator.
 {{!RFC5280}} limits this field to a maximum of 20 octets.
 The serial number MUST be unique
 for each certificate issued by a given CA (i.e., the issuer name