float format with fixed decimals discards sign

[benaryorg]

I'm not sure how to word that, and I think the code describes it better.
Effectively as per title the latter discards the sign of negative numbers.

This happens on both jq 1.8.1 and 1.7.1.

Without Decimals Specified

include "printf";

0.2, -0.2
	| printf("%f")

"0.2"
"-0.2"

With Decimals Specified

include "printf";

0.2, -0.2
	| printf("%.2f")

"0.20"
"0.20"