fix(ui5-popover): Calculate max content height (#3386)

Resolves #3131

This fix steps on the following commit: e35cc1a
It enhances it in a way that Popover.MIN_OFFSET is taken into account into Popover's
maxContentHeight.
Popover.MIN_OFFSET is used when calculating the offset of the Popover from the top, but has never been extracted from the content's height.

packages/main/src/Popover.js

@@ -562,7 +562,7 @@ class Popover extends Popup {
 			}
 		}
 
-		this._maxContentHeight = maxContentHeight;
+		this._maxContentHeight = maxContentHeight - Popover.MIN_OFFSET;
 
 		const arrowPos = this.getArrowPosition(targetRect, popoverSize, left, top, isVertical);