ISSUE_TEMPLATE/bug_report: upstream note

Signed-off-by: William Woodruff <[email protected]>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -7,6 +7,8 @@ assignees: ''
 
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+**IMPORTANT: Do not file reports about *specific* sites breaking when others continue to work. This indicates an upstream error that `ff2mpv` cannot fix and must be raised upstream instead.**
+
 **IMPORTANT: Please check the [Common problems](https://github.com/woodruffw/ff2mpv/wiki/Common-problems) page for debugging tips before submitting an issue. Duplicates of any information on that page will be closed.**
 
 **IMPORTANT: Please fill out every section below. Bug reports with missing information will be