Tiny fixes for the plot tutorial

[core-man]

Description of proposed changes

See https://en.wikipedia.org/wiki/Hypocenter:

A hypocenter (or hypocentre) is the point of origin of an earthquake or a subsurface nuclear explosion.

"the locations of the hypocenters of the earthquakes" seems a little repeated because hypocenter is actually the location of an earthquake. So it's better to remove "of the hypocenters".

Related to #983 and #996.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[core-man]

/format

[seisman]

Could you also change argument to parameter in this tutorial, as discussed in #886.

[core-man]

Could you also change argument to parameter in this tutorial, as discussed in #886.

Done in fb76425.

[seisman]

Line 64: Change "the color" to "the color parameter".

[core-man]

Line 64: Change "the color" to "the color parameter".

done in 552aa5c.