In your local repository, with the COMMIT-5 checkouted, execute the following command:
git rebase -i COMMIT-1
An editor will open with something like this:
pick COMMIT-2 COMMIT-2-MSG
pick COMMIT-3 COMMIT-3-MSG
pick COMMIT-4 COMMIT-4-MSG
pick COMMIT-5 COMMIT-5-MSG
# Rebase xxxxx..xxxxx onto xxxxx
#
# Commands:
# p, pick = use commit
# r, reword = use commit, but edit the commit message
# e, edit = use commit, but stop for amending
# s, squash = use commit, but meld into previous commit
# f, fixup = like "squash", but discard this commit's log message
# x, exec = run command (the rest of the line) using shell
# d, drop = remove commit
Change "pick" to "drop" in COMMIT-2 line, save, close the editor and the commit-2 will be removed from the history (run "git log" to confirm). Push to Gerrit.
Note: To avoid this situation, never send several commits in a row to Gerrit. Always work your commits parallely (more info here).