update pico-serprog to new revision

this merges the fix from:
https://codeberg.org/libreboot/pico-serprog/pulls/1



however, PRs are not to be sent there. riku merged it in
his repository, and i pulled it in the mirror hosted
on libreboot codeberg

Signed-off-by: Leah Rowe <leah@libreboot.org>

config/git/pico-serprog

 {pico-serprog}{
-	rev: 3d573a01c4b8f69fb0474f95d2627db824d26e46
+	rev: e75e3a20e63269a5e3189bc2e49a6a81d45a636a
 	loc: pico-serprog
 	url: https://codeberg.org/libreboot/pico-serprog
 	bkup_url: https://git.disroot.org/libreboot/pico-serprog