Fix hcsshim commit detection

Hack with space in grep, so it won't match github.com/Microsoft/hcsshim/test

Signed-off-by: Shengjing Zhu <zhsj@debian.org>

.github/workflows/ci.yml

@@ -199,7 +199,7 @@ jobs:
           set -o xtrace
           mingw32-make.exe binaries
           bindir="$(pwd)"
-          SHIM_COMMIT=$(grep Microsoft/hcsshim vendor.conf | awk '{print $2}')
+          SHIM_COMMIT=$(grep 'Microsoft/hcsshim ' go.mod | awk '{print $2}')
           cd ../../Microsoft/hcsshim
           git fetch --tags origin "${SHIM_COMMIT}"
           git checkout "${SHIM_COMMIT}"