Update high_availability.md (#4878)
Update high_availability.md (#4878)

Remove double "don't have" in "Enable Concurrent Processing" section.

Signed-off-by: Peter Malmgren <a1a9a8389ecb9a31bb61dc1365d9dc3543a792bd@zapier.com>
argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd,argoproj/argo-cd