DOC: Add header to test_writing.rst

[gustavocmaciel]

Location of the documentation

https://github.com/pandas-dev/pandas/blob/master/doc/source/development/test_writing.rst

Documentation problem

The test_writitng.rst file doesn't have the standard header.

Suggested fix for documentation

This can be fixed by adding {{ header }} at the beginning of the file.

[jorisvandenbossche]

Is it a problem that this header is not present in this file?

[gustavocmaciel]

I wouldn't call this a problem, per se, but since all the .rst files contain this header, it looks like there's a standard, am I right?

[jorisvandenbossche]

Yes, but it's only needed for pages that actually have ipython code blocks that get executed (and this page doesn't have that) + there is also an issue about removing this header -> #28038

[gustavocmaciel]

Yeah there's a full discussion about it. Thanks for clarifying!