pygmt.config: Correctly resetting to default values that contain whitespaces

[seisman]

Description of proposed changes

Fixes#2298

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 wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.
• Use underscores (not hyphens) in names of Python files and directories.

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

[willschlitzer]

Is a test being added to use this whitespace-containing FORMAT_DATE_MAP or is this sufficient to be used on other tests to make sure that whitespace can work?

[seisman]

is this sufficient to be used on other tests to make sure that whitespace can work?

Yes, please see #2298 (comment)

[weiji14]

Thanks @seisman, good catch on finding the whitespace issue during the pygmt.config reset, should have caught this earlier in #1487.

Oh, and Happy Chinese New Year 🐇🧨