schema-kas.json: Fix dialect URL

Use the proper one according to
https://json-schema.org/understanding-json-schema/reference/schema.html.
Will help jsonschema to find the right validator.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/schema-kas.json

@@ -1,5 +1,5 @@
 {
-    "$schema": "https://json-schema.org/draft-04/schema",
+    "$schema": "http://json-schema.org/draft-04/schema#",
     "$id": "https://github.com/siemens/kas/blob/master/kas/schema-kas.json",
     "title": "kas configuration",
     "description": "kas, a setup tool for bitbake based projects",