Update AVL.java

[Logesh314]

Correction in calculation of height of the root node

Issue:

Given code incorrectly gives output as 3 for root node height when the number of nodes are 100 and 1000.

which is not correct as log base 2 of 1000 and 100 is 9.97 and 6.64.

Corrected code:

It gives 9 and 6 as output for 1000 and 100.