Grammatical adjustments of `search index page` to resolve issue #9402

[activus-d]

Issue Summary

Corrections to the grammar in Search index page section of the Usage guide. This will enhance readability and resolve issue #9402.

[squash-labs[bot]]

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Test this branch here: https://activus-dgrammatical-adjustmen-ekubq.squash.io

[thibaudcolas]

@activus-d personally I find this new variant just ends up with a repetition that hurts readability. Let’s keep the existing one!