fix data race in x509->response

[tarunKoyalwar]

Proposed Changes

• when running nuclei with race detector -race it detected a data race in tlsx specifically due to append() function
• closes data race in tlsx due to "Convertx509toResponse()" #330

Possible Reason

• this happens randomly (50%) even with race detector on . and issue seems to be with how append() function internally behaves i.e
  append(arr , elem) when using append new allocated slice is only returned if elem does not fit into existing array arr . if arr has enough space to fit elem then no new memory is allocated and arr itself is returned .
  our unexpected way of using append(arr,elem) was the cause but is now resolved since we are creating new slice and not using append for that

[tarunKoyalwar]

• tested x10 times no data race was detected

$ cat ~/test-templates/newips.txt | go run -race  . -t ~/test-templates/vhost-enum-flow.yaml

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.0.0-dev

		projectdiscovery.io

[INF] Current nuclei version: v3.0.0-dev (development)
[INF] Current nuclei-templates version: v9.6.1 (latest)
[INF] New templates added in latest release: 198
[INF] Templates loaded for current scan: 1
[INF] Targets loaded for current scan: 20
[INF] Running httpx on input host
[INF] Found 20 URL from httpx
[vhost-enum-flow] [http] [info] https://3.98.63.202/ [VHOST: uberflip.com, SC: 404, CL: 9607]
[vhost-enum-flow] [http] [info] https://52.60.165.183/ [VHOST: uberflip.com, SC: 404, CL: 9599]
[vhost-enum-flow] [http] [info] https://104.16.100.52/ [VHOST: hackerone.com, SC: 302, CL: 92]

[dogancanbakir]

LGTM.
Couldn't repro the issue.