Remove unused stuff

[jedelbo]

What, How & Why?

This code was used in migration code that was removed earlier.

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed.

[coveralls-official]

Pull Request Test Coverage Report for Build github_pull_request_282426

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 66 unchanged lines in 14 files lost coverage.
• Overall coverage increased (+0.06%) to 90.584%

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Files with Coverage Reduction	New Missed Lines	%
test/test_dictionary.cpp	1	99.85%
src/realm/array_string.cpp	2	85.04%
src/realm/db.cpp	2	93.13%
src/realm/object-store/shared_realm.cpp	2	93.74%
src/realm/query_engine.hpp	2	93.94%
src/realm/sort_descriptor.cpp	3	93.8%
src/realm/sync/client.cpp	3	90.75%
src/realm/sync/noinst/server/server_history.cpp	3	67.63%
src/realm/sync/noinst/client_impl_base.cpp	4	85.42%
src/realm/sync/transform.cpp	4	61.68%

Totals
Change from base Build github_pull_request_281750:	0.06%
Covered Lines:	233534
Relevant Lines:	257808

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💛 - Coveralls