azurerm_public_ip: Clarify error message (#10533)

Fixes #10285

azurerm/internal/services/network/validate/public_ip.go

@@ -8,7 +8,7 @@ import (
 func PublicIpDomainNameLabel(v interface{}, k string) (warnings []string, errors []error) {
 	value := v.(string)
 	if !regexp.MustCompile(`^[a-z][a-z0-9-]{1,61}[a-z0-9]$`).MatchString(value) {
-		errors = append(errors, fmt.Errorf("%s must contain only lowercase alphanumeric characters, numbers and hyphens. It must start with a letter and end only with a number or letter", k))
+		errors = append(errors, fmt.Errorf("%s must contain only lowercase alphanumeric characters, numbers and hyphens. It must start with a letter, end only with a number or letter and not exceed 63 characters in length", k))
 	}
 	return warnings, errors
 }