deps: remove (indirect) dependency to mailru/easyjson #87

Job	Run time
Lint	36s
Unit tests (ubuntu-latest, stable)	35s
Unit tests (ubuntu-latest, oldstable)	31s
Unit tests (windows-latest, oldstable)	1m 11s
Unit tests (macos-latest, oldstable)	26s
Unit tests (macos-latest, stable)	43s
Unit tests (windows-latest, stable)	1m 3s
	5m 5s

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