encoding/openapi: correct typo

Change-Id: I864b86c333069e7e1cacf02ed9d140e13c29ad2a
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2461
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/encoding/openapi/testdata/simple-filter.json b/encoding/openapi/testdata/simple-filter.json
index 8760bcd..0acf4a4 100644
--- a/encoding/openapi/testdata/simple-filter.json
+++ b/encoding/openapi/testdata/simple-filter.json
@@ -5,7 +5,7 @@
       "version": "v1"
    },
    "components": {
-      "schema": {
+      "schemas": {
          "MyStruct": {
             "type": "object",
             "required": [