Audio Description: Incorporate association suggestions from #4509 review

[kfranqueiro]

This implements suggestions from Mike in #4509 (comment):

1.2.3: I think this should also be "one or more", just like you did with 4.1.2. For instance, one could both add narration in the soundtrack and add audio descriptions. I do think we should strip out the "Using any player that supports audio and video. That seems like a nonsensical bullet, given the circumstances. The new G226 technique makes what I think is inferred here much more explicit.

1.2.5 & 1.2.7: I think we should also strip out the unlinked generic bullet for same reasons as 1.2.3

There was a bit of ambiguity here regarding how widely to remove "Using any player that supports audio and video", as it appears both in instances involving the recently-added G226 and also in instances without. I removed it in all instances based on Mike's suggestion to also remove it in 1.2.7, which only has an instance without G226, but I'm wondering if we might actually want to leave it in those instances.

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