Fix for DNS service being canceled (#18670)

#### Why I did it
To fix `resolv-config.service` being cancelled:
`resolv-config.service` is started from `hostcfgd` each time there is an [update to the dns configuration or during the start of hostcfgd.
](https://github.com/sonic-net/sonic-host-services/blob/6fce4781da508709f11be595e3c7048ffd3138cb/scripts/hostcfgd#L1406) When we perform `config reload` because `hostcfgd` is restarted `resolv-config.service` is also restarted, but due to dependency of [`resolv-config.service` on `sonic.target`](https://github.com/sonic-net/sonic-buildimage/blob/ed839c65055c3cbb446ddabdc9c15b0684988139/files/image_config/resolv-config/resolv-config.service#L5)  `systemd` also tries to restart `resolv-config.service` causing cancellation of one of the instances of `resolv-config.service`. This fix removes the dependency of `resolv-config.service` on `sonic.target`

#### How I did it
By removing the `BindsTo` and `WantedBy` dependency to `sonic.target` the service is not restarted upon `config reload` by `systemd` anymore, which would solve the issue of the service being cancelled.

#### How to verify it
No occurrence of `Job for resolv-config.service canceled.` in `syslog` after this change is considered

files/image_config/resolv-config/resolv-config.service

@@ -2,7 +2,6 @@
 Description=Update DNS configuration
 Requires=config-setup.service
 After=config-setup.service
-BindsTo=sonic.target
 After=sonic.target
 StartLimitIntervalSec=0
 
@@ -11,5 +10,3 @@ Type=oneshot
 RemainAfterExit=yes
 ExecStart=/usr/bin/resolv-config.sh start
 
-[Install]
-WantedBy=sonic.target