update openwhisk tag -> 9b768646b31928cd4ca02d2e4dcc5ba95ad5494b (#272)

- Invoker now checks for 98% used disk space before it stops invoking actions. Before it was 85% which caused github actions often to fail due to their small disks.

Author: Luke-Roy-IBM

tools/travis/setup.sh

@@ -31,7 +31,7 @@ cd $HOMEDIR
 git clone  https://github.com/ibm-functions/openwhisk.git openwhisk
 cd openwhisk
 
-git checkout 03ce08c5b3fdac1a6dd3ae59f893e07cdc8628a2
+git checkout 9b768646b31928cd4ca02d2e4dcc5ba95ad5494b
 
 ./tools/travis/setup.sh