Fix typo. Location=top/left/right/etc while FormFactor=horz/vert.

While writing documentation for develop.kde.org, I noticed there was a bug in one of the examples. Then I realized there was a bug in the kickoff code I copied from.

• https://api.kde.org/frameworks/plasma-framework/html/classPlasma_1_1Types.html

While this patch will fix the bug, the button looks uglier. Should we just remove the switch to "widgets/panel-background"?