Fix explain_array.rst_ links in docs

**Description of the problem**

Currently, the documentation pages for ```filter1d```, ```gmtmath```, ```gmtregress```, ```grdinterpolate```, ```histogram```, ```pshistogram```, ```makecpt```, and ```sample1d``` include doc/rst/source/explain_array.rst_, which demonstrates the use of options for creating 1-D arrays via ```gmtmath```.

Here is an example of the [generate 1D array section in the makecpt docs](https://docs.generic-mapping-tools.org/6.1/makecpt.html#generate-1d-array).

I think the 1D array section only makes sense in the ```gmtmath``` docs and would like to submit a PR with that section removed from the other modules' documentation.