CATROID-1481 Fix bug in 'Single tap at' brick

[dorianpercic]

https://catrobat.atlassian.net/browse/CATROID-1481
When brick coordinates added and read with e.g. 'Show variable' brick at runtime, then the x and y coordinate had one value less than previously assigned.
This is a bug in the libgdx library. In our version of libgdx the Camera.unproject() method, with which we come from the screen coordinates back to the stage coordinates, calculates y like that: y = Gdx.graphics.getHeight() - y - 1;. The -1 is unnecessary and in the Camera.project() function, it is not added to the worldcoordinates. However in the new version of libgdx, y is calculated like that: y = Gdx.graphics.getHeight() - screenCoords.y - viewportY;, which would be correct (see https://github.com/libgdx/libgdx/blob/master/gdx/src/com/badlogic/gdx/graphics/Camera.java#L195C1-L195C99). In this bug fix I just added +1 to the y coordinate when touch is applied. Furthermore I applied Math.round() for both x and y, in order to fix rounding errors on the one hand and on the other fix the off-by-one error for the x coordinate.

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