fix typo: vender should be vendor

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

site/docs/maintain/index.md

@@ -153,7 +153,7 @@ visit: <https://doc.coreboot.org/northbridge/intel/haswell/mrc.bin.html> - the
 handling of this, in Libreboot, is based largely on the information there.
 
 This contains the Intel MRC firmware, auto-downloaded during build
-by `script/update/vender/download`.
+by `script/update/vendor/download`.
 
 In some cases, libre MRC firmware is also available, and provided
 by Libreboot as an alternative choice.