[cleanup] Remove some unused code #7225

Job	Run time
Protobuf Backward Compatibility	11s
Cargo Nextest (Linux)	15m 8s
Cargo Nextest (Linux Nightly)	15m 13s
Cargo Clippy	8m 47s
Cargo Nextest (MacOS)	11m 54s
Cargo Deny	30s
Cargo Fmt	22s
Themis	44s
Rust Doctests	11m 37s
Lychee Lints	7s
Protocol Schema	14m 20s
Backward Compatibility	11m 2s
Database Migration	11m 24s
Genesis Changes	9m 28s
Sanity Checks	6m 1s
Style	36s
Upgradability	11m 22s
Cargo Audit	19s
Non-default Configuration Builds	1m 13s
Unused Dependencies	6m 47s
Windows check for building public libraries	4m 26s
Upload Coverage	22s
Generate Coverage Artifact (unit, unit)	2m 2s
Generate Coverage Artifact (integration, unit integration)	2m 41s
	2h 26m 36s

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