Mark xarray shading test fail for GMT<=6.1.1

[seisman]

Description of proposed changes

The xarray shading issue in #364 was fixed by upstream GMT in GenericMappingTools/gmt#4328.

This PR updates the pytest xfail condition, so that the xarray shading test is expected to xfail only for GMT<=6.1.1.

Closes #364.

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.

[weiji14]

Looks good! In terms of issues #364 and #638, do we want to:

1. have this PR close them automatically (and have users install the GMT dev version using conda install -c conda-forge/label/dev gmt since Bump GMT from 6.2.0.dev1+07a16c2 to 6.2.0.dev2+8a4275f conda-forge/gmt-feedstock#108 is merged).
2. wait until GMT 6.2.0 is released then manually close those two issues?

Also, what do you think about making a PyGMT v0.2.1 release soon-ish? There's a lot of good new documentation!

[seisman]

1. have this PR close them automatically (and have users install the GMT dev version using conda install -c conda-forge/label/dev gmt since conda-forge/gmt-feedstock#108 is merged).
2. wait until GMT 6.2.0 is released then manually close those two issues?

Both are OK for me. I think closing them now makes us easy to track high-priority issues.

Also, what do you think about making a PyGMT v0.2.1 release soon-ish? There's a lot of good new documentation!

Yes, that's why I want to push the merging of PRs like #480 and #482.

[seisman]

BTW, I'm not sure if #638 is fixed by the upstream GMT updates. We need feedbacks from the user.

[weiji14]

1. have this PR close them automatically (and have users install the GMT dev version using conda install -c conda-forge/label/dev gmt since conda-forge/gmt-feedstock#108 is merged).
2. wait until GMT 6.2.0 is released then manually close those two issues?

Both are OK for me. I think closing them now makes us easy to track high-priority issues.

BTW, I'm not sure if #638 is fixed by the upstream GMT updates. We need feedbacks from the user.

Let's just close #364 for now (but keep it pinned), and leave #638 open for a bit longer

Also, what do you think about making a PyGMT v0.2.1 release soon-ish? There's a lot of good new documentation!

Yes, that's why I want to push the merging of PRs like #480 and #482.

Cool, I've got a lot on my plate but will try and get on top of those.