meta: drop issue_template

The contents do not apply anymore now that the switch to Github issue
has been decided.

Signed-off-by: Jo-Philipp Wich <[email protected]>

.github/issue_template

@@ -1,13 +0,0 @@
-This repository is a mirror of our main repo at https://git.openwrt.org/openwrt/openwrt.git
-It is for reference only and is not active for checkins or for reporting issues.
-
-All issues should be reported at: https://bugs.openwrt.org
-
-Please do not open any NEW issue here - we will be closing the Github issues
-capability in the near future.
-
-We will continue to accept Pull Requests here as described in the repo description.
-
-Close this now and click here: https://bugs.openwrt.org
-
-Thankyou for your co-operation.