Fix documentation: use 'update' for updating a library

Signed-off-by: Matthias Maennich <[email protected]>
Change-Id: Iea0e44206a49f90ccf3f5107f1253e4b493ce54d
diff --git a/README.md b/README.md
index cf82576..ca97350 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@
 Update a library:
 
 ```shell
-tools/external_updater/updater.sh check ${LIBNAME}
+tools/external_updater/updater.sh update ${LIBNAME}
 ```
 
 LIBNAME can be the path to a library under external/. E.g. kotlinc, or