fix(schematics): correct path to ng-update entry-point (#10850)

Author: jelbourn

src/lib/package.json

@@ -31,7 +31,7 @@
   },
   "schematics": "./schematics/collection.json",
   "ng-update": {
-    "migrations": "./schematics/migration.json",
+    "migrations": "schematics/migration.json",
     "packageGroup": [
       "@angular/material",
       "@angular/cdk",