fix(rm): Fix CAST_TO_BLOCK_SCALED initialization
Initialization of OpCastToBlockScaled in SubgraphTraverser was incorrectly trying to pull the scale from the second input instead of the second output.
The code has been changed to look for scale_out_index in the output
list instead.
Signed-off-by: Ian Tayler Lessa ian.taylerlessa@arm.com