STYLE : Update metaschema in json_schemas to avoid deprecated warning

python_src/diapotb/share/json_schemas/schema_MultiSlc.json

 {    
-    "$schema": "http://json-schema.org/schema#",
+    "$schema": "http://json-schema.org/draft-07/schema#"
     "title": "JSON SCHEMA for MultiSlc",
     "description": "JSON organization for the script SAR_MultiSlc.py",
 

python_src/diapotb/share/json_schemas/schema_MultiSlc_IW.json

 {    
-    "$schema": "http://json-schema.org/schema#",
+    "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "JSON SCHEMA for MultiSlc",
     "description": "JSON organization for the script SAR_MultiSlc_IW.py",
 

python_src/diapotb/share/json_schemas/schema_S1IW.json

 {    
-    "$schema": "http://json-schema.org/schema#",
+    "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "JSON SCHEMA for DiapOTB S1 IW chain",
     "description": "JSON organization for the script diapOTB_S1IW.py",
 

python_src/diapotb/share/json_schemas/schema_S1SM.json

 {    
-    "$schema": "http://json-schema.org/schema#",
+    "$schema": "http://json-schema.org/draft-07/schema#",
     "title": "JSON SCHEMA for DiapOTB S1 SM chain",
     "description": "JSON organization for the script diapOTB.py",