Remove the spacer would have been my first recommendation, but you should probably check the chain line.

You can eyeball it pretty easily-
Shift to the middle ring-
If an odd number of cogs in the rear, the middle one should line up exactly for a "straight" chain. Shifting to each adjacent cog should show the chain runing at a slight angle. These angles should be the same amount, but opposite side.
IF an even number of cogs, eliminate the "middle cog" from the above step and use the 2 "most middle" cogs.
IF it looks like you'd have a better chain line by removing the spacer, remove it.

They also make thinner spacers for this.