Remove getdkan/locker from dependencies (#4022)

Author: paul-m

composer.json

@@ -17,7 +17,6 @@
         "getdkan/csv-parser": "^1.3.0",
         "getdkan/file-fetcher" : "^4.2.1",
         "getdkan/harvest": "^1.0.0",
-        "getdkan/locker": "^1.1.0",
         "getdkan/procrastinator": "^4.0.0",
         "getdkan/rooted-json-data": "^0.1",
         "getdkan/sql-parser": "^2.1.0",