Follow-up from "Advanced Search: Adapt reindexing to multiple indices support"

The following discussion from !50267 (merged) should be addressed:

• @euko started a discussion: (+1 comment)

  note: we should remove these bootstrap color utility classes and use their gl-* equivalents e.g.,

            .form-text.gl-text-gray-600

  The same goes for .text-danger and all others in this partial.

  We could open a separate issue to do the conversion to keep this MR focused. What do you think?