fix: remove matchedDN and diagnosticMessage on SearchResponseEntry

Following some LDAP UI and Wireshark, these two elements should not be
found inside a SearchResponseEntry (matchedDN doesn't make sense on this
kind of message).

Also, following https://ldap.com/ldapv3-wire-protocol-reference-search/,
I didn't found anything about them:

```
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
     objectName      LDAPDN,
     attributes      PartialAttributeList }

PartialAttributeList ::= SEQUENCE OF
       partialAttribute PartialAttribute

LDAPDN ::= LDAPString
           -- Constrained to  [RFC4514]

LDAPString ::= OCTET STRING -- UTF-8 encoded,
              -- [ISO10646] characters

PartialAttribute ::= SEQUENCE {
     type       AttributeDescription,
     vals       SET OF value AttributeValue }

AttributeDescription ::= LDAPString
           -- Constrained to
           -- [RFC4512]

AttributeValue ::= OCTET STRING
```

response.go

@@ -241,9 +241,6 @@ func (r *SearchResponseEntry) packet() *packet {
 	}
 	resultPacket.AppendChild(attributesPacket)
 
-	// Add optional diagnostic message and matched DN
-	addOptionalResponseChildren(resultPacket, WithDiagnosticMessage(r.diagMessage), WithMatchedDN(r.matchedDN))
-
 	replyPacket.AppendChild(resultPacket)
 	return &packet{Packet: replyPacket}
 }