[Doc]: relpos is not valid for FancyArrowPatch

[jason-sachs]

Documentation Link

https://matplotlib.org/stable/api/text_api.html

Problem

arrowprops section states

Valid keys for FancyArrowPatch are:
...
relpos

but relpos is not a valid kwarg for FancyArrowPatch.

Suggested improvement

Fix so that the docs state allowable keys. I can't figure out when relpos is allowed and when it is not.

Matplotlib Version

3.4.3

[timhoffm]

This seems like a leftover from removing YAArrow (#4178).

The arrowprops docstring is outdated in multiple ways:

• the width, headwidth headlength, shrink, frac parameters are only allowed if there is no "arrowstyle". But they are ignored - should probably be deprecated.
• Three are now more arrowstyles available from FancyArrowPatch.
• relpos is not a FancyArrowPatch attribute. It's handled explicitly - functionality to be inferred from the code.

[timhoffm]

Closed by #21743.