ISSUE_TEMPLATE: 'nix run' -> 'nix-shell -p'

'nix run' is an experimental command.

.github/ISSUE_TEMPLATE.md

···
 
 ## Technical details
 
-Please run `nix run nixpkgs.nix-info -c nix-info -m` and paste the result.
+Please run `nix-shell -p nix-info --run "nix-info -m"` and paste the result.

.github/ISSUE_TEMPLATE/bug_report.md

···
 Add any other context about the problem here.
 
 **Metadata**
-Please run `nix run nixpkgs.nix-info -c nix-info -m` and paste the result.
+Please run `nix-shell -p nix-info --run "nix-info -m"` and paste the result.
 
 Maintainer information:
 ```yaml