drop reference to an undefined variable (#1040)

.github/workflows/checks.sh

diff --git a/.github/workflows/checks.sh b/.github/workflows/checks.sh
index b1845e3..1261531 100755
--- a/.github/workflows/checks.sh
+++ b/.github/workflows/checks.sh
@@ -22,5 +22,3 @@
 if [ -n "${BUILD_DISTRO:-}" ] ; then
     bazel build  //distro:distro
 fi
-
-exit "${exit_code}"