Remove unnecessary code to unset a given fd in catcpserver

Remove unnecessary code to unset a given fd in catcpserver

After reading data from file descriptor, we set the readFds again.
so it is not required to remove a given file descriptor from a set.

Change-Id: I8c7a72b14bcce2f1a513cc6085d4113fa8fea9b1
Signed-off-by: hyuna0213.jo <hyuna0213.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/15731
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: jihwan seo <jihwan.seo@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>