schema: schema attribute tweak

From the json-schema website:
  The possibility to declare $schema without specific version
  (http://json-schema.org/schema#) was deprecated after Draft 4 and
  should no longer be used.

Set the version to draft-07 as not all validators support 2019-09 yet
and no features from 2019-09 are required.

For additional reading:
  https://json-schema.org/understanding-json-schema/reference/schema.html#the-schema-keyword

Change-Id: If88639d6db4e67088660a928a33881fd25cc6cd3
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/schemas/global.json b/schemas/global.json
index acf5a2d..3b870ad 100644
--- a/schemas/global.json
+++ b/schemas/global.json
@@ -1,5 +1,5 @@
 {
-    "$schema": "http://json-schema.org/schema#",
+    "$schema": "http://json-schema.org/draft-07/schema#",
     "anyOf": [
         {
             "type": "array",