start: clarify rel. between `exp run` and `repro`.

[iesahin]

This is reported by @tapadipti (Related: iterative/example-repos-dev#98)

4. If you used dvc repro before section in the doc is a little unclear. Does dvc exp run replace dvc repro? If yes, can we state this clearly? Also would be great to change this statement We use dvc repro to run the pipeline... to dvc repro runs the pipeline...

[shcheklein]

Could that section be removed completely?

[iesahin]

My intention in #3051 is also to remove it completely, because dvc exp init allows a "pipeline-free" experimentation, to an extent, and without pipelines, we don't need to mention dvc repro. @shcheklein

[iesahin]

I've removed the section in #3051.

[jorgeorpinel]

I no longer see the section in https://dvc.org/doc/start/experiments . Can we close this @iesahin ? Thanks

[iesahin]

Closing the issue after #3155.