fix(material/schematics): add clarification about directory path format for MDC migration schematic (#25969)

Author: amysorto

src/material/schematics/ng-generate/mdc-migration/schema.json

@@ -9,7 +9,7 @@
       "format": "path",
       "description": "Workspace-relative path to a directory which will be migrated.",
       "alias": "d",
-      "x-prompt": "Limit the migration to a specific directory? (Enter directory or leave blank for all directories)"
+      "x-prompt": "Limit the migration to a specific directory? (Enter the relative path such as 'src/app/shared' or leave blank for all directories)"
     },
     "components": {
       "type": "array",