ICU-20469 Updating how to control ucadata type in userguide.

diff --git a/docs/userguide/icu_data/buildtool.md b/docs/userguide/icu_data/buildtool.md
index cebde5e950605c439cb8b4e040f608ccc89ca478..839db06c4faa0ad394549b6ee4fa35365e4d51d8 100644 (file)
--- a/docs/userguide/icu_data/buildtool.md
+++ b/docs/userguide/icu_data/buildtool.md
@@ -606,14 +606,11 @@ for common characters but arbitrary for others.  For more information, see
 By default, the unihan version is used.  The unihan version of the data file
 is much larger than that for implicithan, so if you need collation but also
 small data, then you may want to select the implicithan version.  To use the
-implicithan version, pass the following command line argument to buildtool:
+implicithan version, put the following setting in your *filters.json* file:
 
-    --collation_ucadata=implicithan
-
-To pass this argument when using configure/make or Windows makedata.mak, set
-it in the `ICU_DATA_BUILDTOOL_OPTS` environment variable:
-
-    ICU_DATA_BUILDTOOL_OPTS="--collation_ucadata=implicithan"
+    {
+      "collationUCAData": "implicithan"
+    }
 
 ### File Substitution