Clean unused stream code

[paskal]

It was supposed to solve #253 but frontend part for it in #357 was never finished, and backend code produces false positive test failures since day 0. The cost of just having this code around is too high, we'll re-add it in case frontend implementation will be finished.

[coveralls]

Pull Request Test Coverage Report for Build 390622761

• 15 of 15 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 83.463%

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Files with Coverage Reduction	New Missed Lines	%
backend/app/notify/notify.go	2	94.29%

Totals
Change from base Build 390570834:	-0.1%
Covered Lines:	5244
Relevant Lines:	6283

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💛 - Coveralls