Correction in OLAP AVG function example result output [CR #634333]

In Using OLAP > Analytical Functions > Windowing > Window Framing > CURRENT ROW concept the correct result output for the OLAP AVG function example is:

• Row [1] = (10 + 50 + 100)/3

• Row [2] = (50+ 100 + 120)/3

• Row [3] = (100 + 120 + 500)/3

• Row [4] = (120 + 500 + NULL)/2

• Row [5] = (500 + NULL + NULL)/1