`FailedCreateServer` error event was removed while it's still being tested

[EmilienM]

In this PR, FailedCreateServer error event was removed while it's still being tested:

cluster-api-provider-openstack/test/e2e/suites/e2e/e2e_test.go

Line 616 in a63ce56

return isErrorEventExists(namespace.Name, mdInvalidAZName, "FailedCreateServer", azError, eventList)

I have no idea how our CI didn't catch that 🤷 but for sure I'll take a look.

Originally posted by @EmilienM in #1753 (comment)