package/leptonica: fix legal info

Commit 5159f656 forgot to update hash of
leptonica-license.txt which changed due to an update in year:
https://github.com/DanBloomberg/leptonica/commit/8193d341dd56aff5fcbbaab8832e7b38f2fede0a

Fixes:
 - http://autobuild.buildroot.org/results/1644512ca52eed1b69d65d3ca145ec0d253888a8



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>