Fix migrations

[zjb0807]

https://github.com/paritytech/polkadot-sdk/blob/30cda2aad8612a10ff729d494acd9d5353294d63/substrate/frame/support/src/migrations.rs#L427-L443

frame_support::migrations::RemoveStorage can't remove StorageValue item.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.43%. Comparing base (c83043a) to head (9e88b12).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2942   +/-   ##
=======================================
  Coverage   48.43%   48.43%           
=======================================
  Files          69       69           
  Lines        9454     9454           
=======================================
  Hits         4579     4579           
  Misses       4875     4875           

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