chore(nano): avoid storage incompatibility when nano is not enabled

[jansegre]

Motivation

The "impossible migration" introduced in #1380 was having an effect on mainnet even though it only affects the nano storage which doesn't exist yet in mainnet.

Acceptance Criteria

• Only include migration if settings.ENABLE_NANO_CONTRACTS

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.74%. Comparing base (156239b) to head (41d1ec9).
⚠️ Report is 2 commits behind head on hotfixes.

Additional details and impacted files

@@             Coverage Diff              @@
##           hotfixes    #1428      +/-   ##
============================================
- Coverage     85.84%   85.74%   -0.11%     
============================================
  Files           430      430              
  Lines         33061    33064       +3     
  Branches       5171     5172       +1     
============================================
- Hits          28381    28350      -31     
- Misses         3648     3672      +24     
- Partials       1032     1042      +10     

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