Percent Visible property on Label node has incorrect description

[jonchun]

Your Godot version:
v3.2.1.stable.official

Issue description:
The Label node's description of "Percent Visible" is incorrect. It actually accepts a float value between 0-1.

Compare with RichTextLabel

URL to the documentation page:
https://docs.godotengine.org/en/stable/classes/class_label.html
https://docs.godotengine.org/en/stable/classes/class_richtextlabel.html