remove more unnecessary checks on trees commands

the trees script already performs these checks

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

include/vendor.sh

@@ -58,7 +58,7 @@ getcfg()
 
 bootstrap()
 {
-	[ -d "$cbdir" ] || x_ ./update trees -f coreboot ${cbdir##*/}
+	x_ ./update trees -f coreboot ${cbdir##*/}
 	for d in uefitool biosutilities bios_extract; do
 		x_ ./update trees -f "$d"
 	done