tour: Incorrect Default High Bound Description in Slicing Documentation

[Aakash686]

The documentation states:
"The default is zero for the low bound and the length of the slice for the high bound."
However, this is misleading. The default high bound should be the length of the array (when slicing an array) or the length of the slice (when slicing a slice).

Suggested Fix:
"The default is zero for the low bound and the length of the array (when slicing an array) or the length of the slice (when slicing a slice) for the high bound."