Fix typo (no functional change)

servers/slapd/schema/cosine.schema

@@ -1190,7 +1190,7 @@ objectclass ( 0.9.2342.19200300.100.4.13 NAME 'domain'
 #
 objectclass ( 0.9.2342.19200300.100.4.14 NAME 'RFC822localPart'
 	SUP domain STRUCTURAL
-	MAY ( commonName $ surname $ description $ seeAlso $ telephonenumber $
+	MAY ( commonName $ surname $ description $ seeAlso $ telephoneNumber $
 		physicalDeliveryOfficeName $ postalAddress $ postalCode $
 		postOfficeBox $ streetAddress $
 		facsimileTelephoneNumber $ internationalISDNNumber $