Rename some documentation/comment references to build_image

build_image was renamed to `cros build-image`.  Update comment strings
and docs referencing it.

BUG=b:287468690
TEST=CQ

Change-Id: I212ecc370952bf1686f523dbc464fc8d173066b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4621770
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/scripts/build_api.py b/scripts/build_api.py
index 5e540e9..b57f72f 100644
--- a/scripts/build_api.py
+++ b/scripts/build_api.py
@@ -166,7 +166,7 @@
     router = router_lib.GetRouter()
     opts = _ParseArgs(argv, router)
 
-    # For build_image, make sure we run with network disabled to prevent
+    # For `cros build-image`, make sure we run with network disabled to prevent
     # leakage.
     if (
         cros_build_lib.IsInsideChroot()