361 update 09 creatingmotionpathsandflowlinesipynb in accordance with suggestions from ms (#362)

* fix the motion path for Hawaii

* get rid of the India-Eurasia example of motion paths

* set the y-axis of rate of motion starts at 0

* Use hot spots to demo reconstructing motion paths to *past* times.

Maria Seton wanted the India-Eurasia example removed because motion
paths are typically used for absolute plate motions (eg, hot spots)
not relative motions.
This reverts commit 13aff44 (which removed the India-Eurasia example),
and transfers the demoing of *past* reconstruction times in the
India-Eurasia example onto the Hawaiian-Emperor hot spot example.

* specify sphinx version in doc-env.yml. github always tried to use ancient sphinx lately.

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Co-authored-by: John Cannon <[email protected]>

Author: michaelchin