doc: android: Fix a typo

%s/than/then

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/android/boot-image.rst b/doc/android/boot-image.rst
index c719b4d..8f247c7 100644
--- a/doc/android/boot-image.rst
+++ b/doc/android/boot-image.rst
@@ -11,7 +11,7 @@
 (like ``zImage`` file) and ramdisk. Sometimes it can contain additional
 binaries. This image is built as a part of AOSP (called ``boot.img``), and being
 flashed into ``boot`` partition on eMMC. Bootloader then reads that image from
-``boot`` partition to RAM and boots the kernel from it. Kernel than starts
+``boot`` partition to RAM and boots the kernel from it. Kernel then starts
 ``init`` process from the ramdisk. It should be mentioned that recovery image
 (``recovery.img``) also has Android Boot Image format.