Message about resync needed

[felipeelia]

Is your enhancement related to a problem? Please describe.

Now that we have two different sync processes, we might need to clarify the resync needed message a bit, to explain which sync is required.

The current message says:

The new version of ElasticPress requires that you run a sync. Please note that some ElasticPress functionality may be impaired and/or content may not be searchable until the reindex has been performed.

Clicking on the link points the user to the new sync page where the full reindex starts immediately. If the user decides to click on the "Sync" submenu item under ElasticPress, they will go to the Sync page where the two options are presented (and they will need the "Delete all Data and Start a Fresh Sync" one).

Describe the solution you'd like

The easiest fix would be adjusting the message. A more complex solution would be either disabling the simple sync completely (useless at this point).

How to test it
Running wp option set ep_need_upgrade_sync 1 will bring back the message.

[felipeelia]

The new version of ElasticPress requires that you delete all data and start a fresh sync. Please note that some ElasticPress functionality may be impaired and/or content may not be searchable until the full sync has been performed.

[felipeelia]

Closed by #2638