fix a grammar mistake - English version

Author: iamaliyousefi

content/en/docs/concepts/services-networking/service.md

@@ -1128,7 +1128,7 @@ spec:
 ```
 
 {{< note >}}
-ExternalName accepts an IPv4 address string, but as a DNS names comprised of digits, not as an IP address. ExternalNames that resemble IPv4 addresses are not resolved by CoreDNS or ingress-nginx because ExternalName
+ExternalName accepts an IPv4 address string, but as a DNS name comprised of digits, not as an IP address. ExternalNames that resemble IPv4 addresses are not resolved by CoreDNS or ingress-nginx because ExternalName
 is intended to specify a canonical DNS name. To hardcode an IP address, consider using
 [headless Services](#headless-services).
 {{< /note >}}