AhoCorasick warning on 100% remote glossaries

Problem/Motivation

AhoCorasick warning about no content.

Steps to reproduce

• Install the module
• Configure Tooltips = None on/admin/config/content/g2/formatting to enable remote glossary
• Configure the API Client on /admin/config/content/g2/api, setting e.g. https://riff.org/g2/entries as the remote glossary base
• Do NOT create any G2 entry
• Create a node, e.g. an article containing a <dfn>ASCII</dfn> reference to create a remote dictionary link
• Observe AhoCorasick warning about the lack of any word in the glossary

Proposed resolution

This is caused by the matcher trying to build its index on a site using a remote dictionary instead of a local one : disable rebuilding the the site is configured to use the API client to a remote dictionary.

Remaining tasks

User interface changes

• Clarify the wording on the Tooltip screen explaining that Tooltip definitions must be None to enable the API Client.
• Provide a default link as an example to avoid issues like #1135328: default remote G2 glossary is empty/has no terms → where the user did not understand the API Client URL format

API changes

None.

Data model changes

Index will no longer be updated on sites using the API client instead of a local glossary.