Remove unnecessary check from compressed instruction decode

Created by: kjprime

The following changes remove a unreachable state in coverage within the decompress file and redundant check. This statement is checking for a value aligning to the last possible option in all cases for truth table for instruction bits 12:10.

Truth table instr16[12:10]

line#  | 12 | 11 | 10
114    |  X   0    0
116    |  X   0    1
118    |  X   1    0
120    |  0   1    1
129    |  1   1    1

I believe checking this statement is redundant and leaving it as a comment increases clarity.