Fix minor typo in error message

Test: None
Change-Id: I0ab2dc776456c32ab9c1ce7470e78f59a40c8d43
diff --git a/core/board_config.mk b/core/board_config.mk
index 4424517..633303f 100644
--- a/core/board_config.mk
+++ b/core/board_config.mk
@@ -992,7 +992,7 @@
 # BOARD_API_LEVEL for vendor API surface
 ifdef RELEASE_BOARD_API_LEVEL
   ifdef BOARD_API_LEVEL
-    $(error BOARD_API_LEVEL must not set manully. The build system automatically sets this value.)
+    $(error BOARD_API_LEVEL must not be set manually. The build system automatically sets this value.)
   endif
   BOARD_API_LEVEL := $(RELEASE_BOARD_API_LEVEL)
   .KATI_READONLY := BOARD_API_LEVEL