upgrading knife to v18.8.68 (#3474)

Signed-off-by: nikhil2611 <nikhilgupta2102@gmail.com>

Author: nikhil2611

components/gems/Gemfile.lock

@@ -794,7 +794,7 @@ GEM
       rack (>= 1.6, < 4.0)
       test-kitchen
       vmware-vra (~> 3.0, >= 3.2.0)
-    knife (18.8.65)
+    knife (18.8.68)
       bcrypt_pbkdf (~> 1.1)
       chef (~> 18.0)
       chef-bin (~> 18.0)