[misc] Improve Issue/PR templates (#11499)

Authored by: seproDev

.github/ISSUE_TEMPLATE_tmpl/3_site_feature_request.yml

@@ -1,5 +1,5 @@
 name: Site feature request
-description: Request a new functionality for a supported site
+description: Request new functionality for a site supported by yt-dlp
 labels: [triage, site-enhancement]
 body:
   %(no_skip)s
@@ -16,9 +16,7 @@ body:
           required: true
         - label: I've checked that all provided URLs are playable in a browser with the same IP and same login details
           required: true
-        - label: I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
-          required: true
-        - label: I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)
+        - label: I've searched the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=is%%3Aissue%%20-label%%3Aspam%%20%%20) for similar requests **including closed ones**. DO NOT post duplicates
           required: true
         - label: I've read about [sharing account credentials](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#are-you-willing-to-share-account-details-if-needed) and I'm willing to share it if required
   - type: input