Auto merge of rust-lang#2700 - RalfJung:begingroup, r=RalfJung

CI: fix begingroup printing

Author: bors

src/tools/miri/ci.sh

@@ -2,7 +2,7 @@
 set -euo pipefail
 
 function begingroup {
-  echo "::group::$1"
+  echo "::group::$@"
   set -x
 }