Remove `snow.DefaultContextTest` #968

Job	Run time
Up-to-date protobuf	20s
Up-to-date mocks	2m 2s
e2e	7m 30s
Protobuf Lint	7s
e2e_existing_network	3m 6s
Fuzz	12m 29s
Up-to-date go.mod and go.sum	16s
Lint	3m 4s
Unit (macos-12)	6m 40s
Upgrade	2m 0s
Unit (ubuntu-20.04)	4m 29s
Unit (ubuntu-22.04)	4m 37s
Unit (windows-2022)	9m 23s
Unit (self-hosted, linux, ARM64, focal)	1m 6s
Unit (self-hosted, linux, ARM64, jammy)	1m 5s
	58m 14s

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