Fix guide incorrectly refers to public/assets/images

[tangposmarvin]

Fix for asset pipeline guide in this line:

In regular views you can access images in the public/assets/images directory like this:

Relates to issue #28387

[rails-bot]

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[vipulnsward]

@tangposmarvin please squash the commits.

[vipulnsward]

@tangposmarvin please add [ci skip] to commit messages in future, so that we don't run CI for doc changes on Travis

[tangposmarvin]

@vipulnsward noted on that, thanks.