Revert to prior CLA language in Definitions.

* modules/openstack_project/files/gerrit/cla.html: There was an
inadvertent modification from the original CLA in the definitions
section. This change reverts to the original CLA language in that
section and also corrects a typo in Section 5.

Change-Id: I26cf8ac4fabe86d045d9247d70d2d9855b4d740d
Reviewed-on: https://review.openstack.org/22507
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins