chore: remove redundant translation line (#6397)

### Description
Remore redundant unused translation line.

### Test plan
No testing needed.

### Related issues
N/A

### Backwards compatibility
Yes

### Network scalability

If a new NetworkId and/or Network are added in the future, the changes
in this PR will:

- [x] Continue to work without code changes, OR trigger a compilation
error (guaranteeing we find it when a new network is added)

locales/base/translation.json

@@ -2831,6 +2831,5 @@
     "selectToken": "Select token",
     "fiatPriceUnavailable": "Price unavailable",
     "tokenDescription": "{{tokenName}} on {{tokenNetwork}}"
-  },
-  "on": "on"
+  }
 }