state=Stable does not check for visibility

[kolkvdta]

Describe the bug
I have recently seen that state=stable does not check visible the same way that state=visible does. I have created a simple test with directly using browser library. The keyword with state=stable passes, while the keyword with state=visible fails.
In the library it states that "| stable | to be both visible and stable. |"

`browser.Wait For Elements State    selector=//xpath[.="text"]    state=stablebrowser.

Wait For Elements State    selector=//xpath[.="text"]    state=visible`

To Reproduce
Steps to reproduce the behavior:

1. setup a test like above in the description
2. Check a simple xpath that is always visible
3. Run the test and put a debug on the first keyword
4. Change the HTML code in the CSS to display: none or add "hidden" to the HTML element.
5. Continue the test run
6. Observe that the state=stable passes
7. Observe that the state=visible fails

Expected behavior
I expect that the stated description of the code for the state=stable works as expected. But it does not check for visibility.
| stable | to be both visible and stable. |