Simplified examples for plotting cross-section and along slope velocity (#420)

* Simplified cross-slope section example

* Simple along-slope velocity example for access-om2-01

* split cross-along slope

* rename

* simplify

* Changes post review for Examples/Along-slope-velocities.ipynb and Examples/Cross-slope_section.ipynb. Ready to be merged.

* better variable names

* normal font size

* delete duplicate

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Co-authored-by: Qing Yee Ellie Ong <qo9901@gadi-login-05.gadi.nci.org.au>
Co-authored-by: Qing Yee Ellie Ong <qo9901@gadi-cpu-bdw-0063.gadi.nci.org.au>
Co-authored-by: Navid C. Constantinou <navidcy@users.noreply.github.com>
Co-authored-by: Qing Yee Ellie Ong <qo9901@gadi-cpu-bdw-0147.gadi.nci.org.au>

Author: 5 people