[SM-1031] Remove SecretsManager & showDDG compile flags (#8610)

Remove old compile flags which should no longer be required, and may even cause issues. secretsManager: false hides the app switcher which is now used for more than just secrets manager.

apps/web/config/selfhosted.json

@@ -7,7 +7,6 @@
     "port": 8081
   },
   "flags": {
-    "secretsManager": true,
     "showPasswordless": true,
     "enableCipherKeyEncryption": false
   }