content/core-concepts/tags: The figure is hard to read

[rakyll]

https://opencensus.io/img/tag-propagation-handdrawn.jpg is hard to read, can we redraw this in the old style to make it more readable?

/cc @odeke-em

[odeke-em]

Roger that @rakyll! The original diagram was deemed unrelatable to non-GCP and Googlers by feedback that we got hence that attempt :) However, if you could update to the old style of drawing, we can use that instead as I am not that great at drawings :)

[odeke-em]

/cc @hvent90 too