website: fixed a command line

The original command line for push under
the "Making iterative improvements based
on feedback" was causing error.
This commite changed it from "git push
original HEAD:refs/for/develop" to
"git push origin HEAD:refs/for/develop"

Change-Id: I27f386f90330135065f5dd33674991af9e82d763
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/61170
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
diff --git a/_pages/contributing.md b/_pages/contributing.md
index e9e3382..b27f285 100644
--- a/_pages/contributing.md
+++ b/_pages/contributing.md
@@ -322,7 +322,7 @@
 Then push the new changes to Gerrit:
 
 ```Shell
-git push original HEAD:refs/for/develop
+git push origin HEAD:refs/for/develop
 ```
 
 If for some reason you no longer have your original workspace, you may pull