refactor(test): remove header dependence from tests

[tac0turtle]

Description

this pr removes all instances of cmtproto.Header{} in tests. Since it is an empty header it is best we dont rely on the type from comet at all for these

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[tac0turtle]

in the future this would use the header service instead of headerInfo from context. This will happen we we do further integration with core api

[julienrbrt]

lgtm, few nits.